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COMPUTERISED ELECTRO-MECHANICAL CONTROL OF THE UWS ASTRONOMICAL TELESCOPE AND THE INTEGRATION OF A MULTI-TASKING TELEVISION SYSTEM
by
FRANK WILLIAM BIRD BSc BTeach
A Thesis submitted for the Degree of Master of Science (Hons) at the University of Western Sydney, May 2005.
DEDICATION To my lovely wife Treve who patiently entered every (well almost) keystroke in this Thesis as I clumsily dictated the content. Her willingness to help, and the many late nights at the keyboard are very much appreciated.
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ACKNOWLEDGEMENTS
I would like to thank all those concerned in making this Thesis possible. In particular I would like to thank Dr. Graeme White who invited me to be involved in the UWS Telescope project and gave me great support and assistance during the project. Thanks also go to my co supervisor Dr Paul Jones and to my supervisor in the latter stages of the project Dr Ragbir Bhathal. I thank UWS Nepean for providing a HECS exemption scholarship and other resources to enable me to complete this Thesis. Finally, I thank my wife for enduring the upheavals and changes household routine which an undertaking such as this inevitably inflicts.
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STATEMENT OF AUTHENTICATION
I declare that to the best of my knowledge, the work described in this Thesis is original, except as acknowledged in the text, and that the material has not been submitted, either in whole or in part, for a Degree at UWS or any other University.
FRANK W BIRD
April 2005
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TABLE OF CONTENTS
Page CHAPTER 1. - Introduction 1.1 Purpose of this Thesis 1 1.2 A brief history of Astronomical Telescopes 1.2.1 Early instrumentation 2 1.2.2 Scientific use of Telescopes and the effects of aberrations 4 1.2.3 Use of mirrors 6 1.2.4 Limitations and developments 8 1.2.5 The UWS Telescope 9 1.2.6 Telescope mountings 10 1.2.7 Equatorial mounts 13 1.2.8 Alt-Azimuth mount 14 1.2.9 Adding a layer of complication to a simple problem of telescope mounting 15 1.2.10 Computer control 18
CHAPTER 2. - Mechanical Resonant Frequencies 2.1 Resonant frequencies 20 2.2 Method used 20
CHAPTER 3. - Aligning the Equatorial Head 3.1 Criterion for long exposure 22 3.2 Alignment method 22 3.3 Altitude adjustment 24 3.4 Azimuth adjustment 26
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CHAPTER 4. - Initial Tracking and Slewing Control System 4.1 Tracking and slewing system 28
CHAPTER 5. - The Video System at the UWS Observatory 5.1 Tasks 31 5.2 Onsite education 31 5.3 Remote viewing 37 5.4 Remote science 38 5.5 Research 39 5.6 Public viewing 40 5.7 A note on Gamma correction 44 5.8 Star-trak 47 5.9 Precautionary note 48
CHAPTER 6. - Engineering Approaches to Telescope Automation 6.1 Go-to 50 6.2 Stepper motor benefits 52 6.3 Stepper motor drawbacks 53 6.4 Brush servo benefits 53 6.5 Brush servo drawbacks 54 6.6 Brushless servo benefits 54 6.7 Brushless servo drawbacks 55
CHAPTER 7. - The Control System at UWS 7.1 Chosen system 56 7.2 Making things easy 58 7.3 Safety 59 v CHAPTER 8. - A Pointing Model 8.1 Options 62 8.2 Observation data 63 8.3 Assessment of pointing model scatter plots 95
CHAPTER 9. – Conclusions and future work 9.1 Current performance 96 9.2 Future work 96 9.2.1 Video System 96 9.2.2 Robotics 97
REFERENCES 98
APPENDIX A - EXTRACTS FROM ACE MANUAL 99
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LIST OF TABLES page Table 1. Spread sheet layout of HA prime unit and correction 87
Table 2. Spread sheet layout of DEC prime unit and correction 94
vii LIST OF FIGURES AND ILLUSTRATIONS page
1. The first known use of instruments in astronomy 2 2. A wood cut of Hans Lippershey taken from Pierre Borel’s 3 De Vero Telescope Inventore, 1655. 3. Galilao demonstrating his first telescope 4 4. Spherical aberrations 5 5. Longitudinal chromatic aberration 5 6. Lateral chromatic aberration 6 7. George Dollond (1774 – 1852) 7 8. The main components of the Great Paris Refractor 8 9. The f10 UWS observatory 9 10. Altitude azimuth and equatorial mounts 11 11. The Great Dorpat Refractor 12 12. Schneider’s Helioscope 13 13. Relative amplitudes of the telescopes resonant frequencies 21 14. Eliminating non-linear scan error using an electronic pattern generator 23 15. Elevation adjustments and resulting error 25 15.1 Increments in Azimuth and the resulting error 26 16. VFO Circuit diagram 29 16.1 Original system hand paddle 30 17. Video patch panel 32 18. Moon Cam mounted on the side of the main frame 35 19. Rear view of the UHF modulators 36 20. YH438C Q video switcher (ACE smart dome control unit below) 39 21. Video system schematic 43 22. Gamma correction curves 45 22.1 1/3 inch CCD camera with adjustable gamma 46 viii 23. Outer-rotor construction of the Dinaserve motors 56 24. Output torque versus speed of the DM/DR series motors 57 25. U-matic idler wheel coupled to encoder below 59 26. Control desk with CCTV monitor 61 27. Scatter plot of HA prime unit versus correction 88 28. Scatter plot of DEC prime unit versus correction 94
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ABSTRACT
Obtaining a very high level of precision and sophistication in automated computer control is now available inexpensively from a variety of hardware and software sources. Applying this automated technology to an astronomical telescope broadens the scope of applications of the instrument, particularly in areas such as photo electrics, CCD imaging and remote control.
The ultimate design goal of the UWS telescope was that of full roboticism, giving access of the facility to off campus clients both in Australia and overseas. The first phase toward full robotic control is automation of the required optical and mechanical parameters, providing precision targeting and object tracking.
This Thesis describes the mechanical aspects of the UWS Telescope and the procedures and equipment involved in its automation, including the drive system, electro mechanical design and associated computer hardware and software. Sample performance test data shows that using a high percentage of inexpensive proprietary robotics components, a very sophisticated and accurate measuring device can be produced.
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CHAPTER 1 - INTRODUCTION
1.1 PURPOSE OF THESIS
This thesis describes and discusses the installation, testing and commissioning of the control system and TV camera systems of the 24 inch, f/10 Ritchy-Chretien telescope of the UWS Observatory at the University of Western Sydney. The intention at the University of Western Sydney (UWS) was to firstly put the telescope under computer control, secondly to have the telescope fitted with various cameras which could be used for teaching and remote viewing (see video system chapter 6) and thirdly to have the telescope controlled robotically over the internet by a distant observer. The telescope at UWS was designed to carry out two principal roles for the centre of astronomy. The first one was to provide a research tool for its undergraduate and early level post graduate students. The second role was to act as a teaching observatory for the University, and to allow the university to interact with the public and with the school sector of Western Sydney. A principal design parameter of the facility was to put TV images into various places around the building and hopefully eventually over the internet. As such, it is appropriate to start this thesis with a brief historical review of the instruments used in astronomy, their mounting systems, their control systems, and how this knowledge was applied to the instrumentation systems at the UWS Observatory.
1 1.2 A BRIEF HISTORY OF ASTRONOMICAL TELESCOPES. 1.2.1 Early instrumentation. Historically, astronomy became a science possibly as early as 3000 years BC. The earliest scientific instruments that are recorded, and that are in collections, consist of plumb bob lines which were used for sighting from one observer to the other. These were used for the practical application of astronomy, namely for navigation, and for surveying for the determination of land etc. after flood. The earliest of these dates back to Egyptian times
.
fig 1. The first known use of instruments in astronomy. (Reproduced from.King 1955).
The first of the instruments that attempted to measure the elevation of an object in the sky came about in the Greek times and one particular instrument called Ptolemy’s Rule, which used the combination of two axes of rotation, the vertical axis and the horizontal axis. This instrument allowed the measurement of both the azimuth and the elevation of the object . The telescope itself as we know it was invented in 1608 by a Dutch optician named Hans Lippershey.
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. fig 2. A woodcut of Hans Lippershey. ( Pierre Borel’s De Vero Telescopii Inventore,1655 .Reproduced from King 1955)
Lippershey patented the concept, although it is reputed that it was actually invented sometime before that, in Holland, as being a mechanism for measuring the strength of an army. In other words it was patented as a military device.
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fig 3. Galileo demonstrating his first telescope (American Museum of Natural History. Reproduced from King 1955)
1.2.2 Scientific use of telescopes and the effects of aberrations
The first scientific use of the telescope was by Galileo in 1610 and his observations are well recorded as they are the basis of the dispute between the Catholic Church, the Pope and Galileo which resulted in Galileo being immortalised. The telescope used by Galileo was a very simple device consisting of a tube with 2 lenses attached, one being a convex lens which converged the light from a distant object to an image and the second, being a negative lens which then translated that image back to the retina of the eye. This optical configuration was by modern standards rather unsatisfactory, although it can still be found in very cheap binoculars and plastic toy binoculars found in Department Stores. The Galilean optical system is still used today in instruments such as opera glasses. The Galilean telescope as it became known has two fundamental limitations. The first one is to do with the eye piece lens which was
4 concave. This lens limited the magnification of the telescope, and also very severely limited the field of view. (The two working in tandem, the greater the magnification, the smaller the field of view). This was a very severe practical limitation. It did however have one very great advantage and that was it left the image as seen through the telescope erect i.e. Images pointing in the same direction as the object. This type of telescope was ideally suited for terrestrial viewing but not necessarily for astronomical viewing. The eye piece was eventually replaced by a positive lens which eliminated the difficulty of field of view and allowed magnifications to go much higher, but did in fact turn the image upside down which is not a problem scientifically but meant that this type of telescope was no longer suited for terrestrial viewing. The other difficulty with the Galilean telescope was the simple convex objective lens. This lens suffered from the standard lens aberrations, the principal one being spherical aberration and the other of concern being chromatic aberration.
fig 4. Spherical aberration.
fig 5. Longitudinal chromatic aberration
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fig 6. Lateral chromatic aberration
Those two are highlighted because they are in fact the most important. The way to eliminate these is to increase the focal ratio, as all of these scale as the f number, indeed some of them scale as the f number squared. Going to larger f numbers meant that the telescope became rather unwieldy, very long and difficult to keep stable and point in the right direction. Combining that with a very narrow field of view meant that trying to acquire the object in the sky was very difficult indeed. The latter problem of spherical and chromatic aberration was solved by George Dollond (McConnell 1992), who discovered and eventually manufactured a lens that would violate the rule laid down by no other than Isaac Newton.
1.2.3 Use of mirrors. Newton’s idea was that dispersive power and refractive index of glass were the same and they could not be separated, and therefore, if a lens was made of sharper curvature the dispersive power of the lens would only be enhanced. This in fact is not true, and Dollond showed that a combination of curvature and dispersive power and refractive index could be put together in such a way that the dispersive power could be turned back on itself by a second lens without eliminating the curvature, so the net result was that the two lenses working together would create an image free from chromatic and spherical aberration. This lens was called the achromatic lens and because there were two of them it was called the achromatic doublet.
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fig 7. George Dollond 1774-1852.(Reproduced from King 1955).
However, probably the greater step forward in optics in terms of astronomical telescopes did in fact come from Isaac Newton who believed that the aberrations of a lens could not be eliminated and so decided to remove lenses from the objective component of the telescope. Newton’s contribution was to use a curved mirror, a concave mirror, to bring light to a focus where it could be then magnified by a series of smaller lenses. This was a key stroke in the development of astronomical telescopes. The next step to follow from that was the placement of a second mirror into the system which turned the light back, and put the eyepiece at the rear of the telescope, a more acceptable place for it. Selecting the correct configuration even returns the orientation of the image to normal. That configuration, called Gregorian, is no longer used in astronomical telescopes but it was at one stage quite fashionable amongst small terrestrial type telescopes.
The other key development in the telescope was the introduction of glass mirrors. This came about towards the end of the 1800’s when it was discovered that mirrors could be produced via the deposition of silver onto glass. Glass is a very hard substrate, it can be worked and shaped with great precision and the thin layer of silver on the top surface made a perfectly good reflecting device. This technology was invented in the 1860’s and was adopted by most of the great telescopes of the first half of the last century including the 60 inch telescope at Mount Wilson, the 100 inch telescope at Mount
7 Wilson and later the 200 inch telescope at Mount Palomar. In passing, it can be noted that the technology for depositing silver onto glass was available at the time of the purchase of the Great Melbourne Telescope. It is considered by many historians that the failure of the Great Melbourne Telescope as a scientific instrument was partly due to the lack of adventuresome engineering in the manufacture and design where the traditional specula metal mirror was adopted in preference to the emerging silver on glass technology. Subsequent attempts to clean and re-polish the specula metal mirror proved to be unsuccessful and as a consequence the instrument was never as powerful as the designers had hoped it would be. 1.2.4 LIMITATIONS AND DEVELOPMENTS The refracting telescope also evolved but reached a practical limit in its size towards the end of the 19th century. The largest refracting telescope ever built was a 50 inch lens which was mounted in Paris for the Great Fair of 1900 and was subsequently dismantled and placed into a box and never used.
fig 8. The main components of the Great Paris Refractor.(Reproduced from King 1955)
The second largest built was the 40 inch telescope at Yerkes observatory in Wisconson, USA and the third largest built was the 36 inch refracting telescope built at Lick Observatory on Mount Hamilton in California. These telescopes are nowadays still in operation but are very much historic in their nature but still used in scientific work. The reflecting telescope however has developed even further and modern instruments such as the Keck 1 and 2 and the European Southern Observatory’s very large telescope called VLT are continuations of the development of the technology. For these very large telescopes the mirrors are segmented into smaller sub mirrors and aligned with piezo electric adaptors. The entire telescope mirror is kept into place by laser holography and the shape of the mirrors themselves are adjusted to allow for
8 atmospheric changes above the telescope using techniques known as adaptive optics. (Max 2003).
fig 9. The UWS OBSERVATORY at the University of Western Sydney,Nepean
1.2.5 THE UWS TELECSOPE
The telescope of the Nepean Observatory at the University of Western Sydney is a much smaller version and much lower technology than the ones just referred to. The telescope at UWS is a 24 inch Cassegrain telescope built along the lines of the Ritchey-Chretien optical system. This design criteria were made by Dr Graeme White who developed the original concept of the UWS Observatory and supervised the construction, as well as the design, construction and installation of the telescope itself. This particular optical design using hyperbolic mirrors eliminates many of the aberrations in the focal plane which cause image distortion such as astigmatism and spherical aberration, but leaves in the image some image distortion and a small amount of curved field. Image distortion does not openly destroy the quality of the image as does the other aberrations, so it is the preferred optical configuration.
9 1.2.6 TELESCOPE MOUNTINGS
Along with the development of the optical telescope comes the development of the mounting for the telescope. The fundamental underlying physics and engineering of telescope mountings is that the telescope must be made to continue to point to the object in the sky with a precision which is comparable with the ability of the telescope to resolve the object. In early days the ability of an instrument to resolve an object was limited to the resolving power of the human eye. It was necessary for instruments without optical aid to have a stability and pointing accuracy of a few minutes of arc, a minute of arc being the limiting resolution of the human eye. Early astronomical instruments did not require a high level of engineering to make them stable for their intended use. An additional problem for the mounting of astronomical telescopes is that the sky is continually moving with respect to the telescope. The motion of an object across the sky is a consequence of the rotation of the earth. This motion is both in altitude and azimuth simultaneously, with the exception of two sets of places on the earth where the motion can in fact be simplified to be one axis rotation. These places are the poles and on the equator. For all other observing places the motion of an object across the sky is a combination of azimuth and elevation change. A first order mechanism to eliminate this difficulty is to tilt one of the axis of the telescope to be parallel with the earth’s axis. To eliminate the motion of one of these axis throughout the observing session, the second axis, the one which is not rotating, is pointed towards the celestial pole. This is the concept of equatorial mounting, where one axis is called the equatorial axis or the polar axis and the other is called the declination axis.
10 fig 10. Note: Items a, b, and c are altitude azimuth designs and for which simultaneous motion in both axes is necessary to track the object in the sky. Items d, e, f and g are equatorial mounts requiring motion in only one axis (Ridpath 1991).
Possibly the most significant development in the equatorial mountings was the Dorpat refractor built by Fraunhofer. This instrument had two axis but mutually perpendicular and was also fitted with significant counter weighting to allow for flexure in the axis. Of great significance was that this telescope, it is believed, was the first time that roller bearings were ever used. Dorpat was instrumental in their development and used them in the support mechanism of the polar axis of the refractor.
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fig 11. The Great Dorpat Refractor (KING 1955)
12 1.2.7 EQUATORIAL MOUNTS The first equatorially mounted telescope was by Scheiner in the early 1600’s. Tyco also used equatorially mounted instruments, although they were not telescopes they were non-optical sighting instruments for his observations. The first equatorial instruments were by Tyco. The first equatorially mounted telescope was by Scheiner.
fig 12. Schneider’s Helioscope (King 1955)
The mounting on the Dorpat telescope is now known as the German Equatorial Mount. There are other hybrids of equatorial mounts. Those hybrids being the English Equatorial Mount, the Fork Equatorial Mount, such as at the twenty four inch telescope at the UWS Observatory and the Yoke Equatorial Mount. A further system, called the Horseshoe, is employed at the Anglo Australian Telescope at the Siding Spring observatory near Coonabarrabran. The difference in these designs allows for different
13 shape telescopes and different latitudes. Some designs are more suited for different latitudes than others e.g. the Fork telescope is very seldom used at the Equator or near the Equator where the angle of the Fork is low to the horizon and vibrations are easily introduced into the system.
1.2.8 ALT-AZIMUTH MOUNT
The simple azimuth telescope mounting used in the very earliest of instruments is still used today in telescopes and underwent a resurgence of interest with the introduction of radio telescopes and computers. A single dish radio telescope has a larger beam in the sky, and as such, the pointing accuracy of these telescopes need not be as accurate as that for optical telescopes thus relaxing some of the engineering design. In early days this computing was done by analogue devices, such as the master equatorial on the Parkes Radio Telescope. The exception to this has been in the last 20 years during which there has been resurgence in optical telescopes back to Alt Azimuth. The intrinsic advantage of the Alt Azimuth is that the mechanical aspects of it are very stable. The weight in an Alt Azimuth mount is carried on a vertical fork so the instrument can be very stable from vibration. The disadvantage of the Alt Azimuth mount is that the telescope has to be driven in both axes simultaneously and at a non-uniform rate. This is quite easily obtained nowadays with the use of computer controlled systems but it is an additional complication which is probably unwarranted in relatively small instruments such as the UWS telescope. An additional complication in large Alt Azimuth telescopes is that the field of view at the eye piece also rotates with the other two motions. This necessitates a third mechanical electro system to drive the camera to rotate on the optical axis of the telescope to compensate for the rotation of the field of view. This means there are 3 systems all of which have to be undertaken very carefully with high level precision computer equipment.
The first of the big Alt Azimuth optical telescopes was actually the Russian telescope called the BTA which was built in the Caucausus Mountains in the 1960’s. It was
14 absolutely a pioneering piece of engineering at the time although it seems historically the telescope has never been a great success, for reasons which may or not have to do with the Alt Azimuth mounting, but more to do with the optical system.
1.2.9 ADDING A LAYER OF COMPLICATION TO A SIMPLE PROBLEM OF TELESCOPE MOUNTING.
The equatorial mount is designed to eliminate the rotation of one axis and to give a uniform rotation on the polar axis as an object is tracked in the sky. This is a theoretical model. There are additional layers of complication which must be taken into account. The first of these is the mechanical construction of the instrument itself. The first and most obvious correction that is necessary is to allow for mechanical flexure in the telescope due to the influence of gravity. This occurs because the angle of the telescope relative to the vertical changes as the telescope follows the object across the sky, which in turn changes the forces due to gravity acting on different parts of the structure. In practice this is corrected assuming the flexure scales as the cosine of the angle of the telescope relative to the vertical. If both axes are not perpendicular then additional corrections need to be built into the tracking system. As stated above the precision with which the telescope must point at the sky and maintain that pointing over the duration of the observation is determined by the resolving power of the telescope. For all telescopes the resolving power (in Radians) is given by :
Resolving power (Theta, in Radians) =1.22 Wave length (Lamda in Metres)/ Aperture diameter (d in Metres). θ=λ/d.
For optical telescopes the Lambda can be approximated to 550 nm and this equation gives - after transformation of units - an angular resolving power of one arc second for
15 a telescope of approximately 100 mm aperture. In practice larger instruments do not improve the resolving power of the telescope (contrary to the above equation) as the turbulence of the earth’s atmosphere limits the resolving power to approximately one arc second. There is considerable debate in the literature about how to improve this limitation, the simplest one being to take the telescope to a high, clear, stable atmosphere or indeed, in the limit, place the instrument into space free from the earth’s atmosphere, such as has been done with the Hubble Space Telescope. The necessity to keep the optical telescope pointing at a one arc-second precision necessitates that all mechanical axis be aligned to that precision i.e. the declination axis needs to be perpendicular to the polar axis to one arc second. This is mechanically difficult to do and a correction to the declination axis throughout the observation is often necessary to eliminate the lack of perpendicularity of these two axes. In addition the polar axis itself must be aligned to the rotation axis of the earth. This must also be done to the same precision. There are standard techniques for doing this. (See chapter on Equatorial Alignment) An additional complication and one which is the major limiting parameter in the operation of optical telescopes is the refraction of the earth’s atmosphere. The earth’s atmosphere has a refractive index of approximately one (Allen 1973) but this is dependant on humidity, temperature and pressure. The atmosphere does in fact refract light that enters it, and the amount of refraction depends on the angle of incidence into the atmosphere. Light coming directly from above at the zenith is not refractive, whereas light coming from angles close to the horizon is refracted upwards by a small amount. The amount of refraction is not just dependent on the angle to the horizon but it is also dependent on the temperature and pressure and in particular the humidity and gaseous content of the atmosphere.
The refraction is also wavelength dependent which means that different coloured objects, stars with different dominant spectral features, are refracted by differing amounts. This is a second order effect but still one which needs to be included. The bottom line is that the refraction is something which works on both the polar axis and the declination axis, and small adjustments are needed in both these axes as the
16 telescope moves towards the horizon. Also it should be remembered that the refraction is dependent on atmospheric conditions, so one particular day to the next, or even hour to hour, the refraction changes and this means the telescope does in fact need to have the capacity to drive (albeit it small amounts), in declination and to have small changes in drive speed in the right ascension to correct for these changing parameters. As well as aligning the pole of the telescope to be parallel with the earth’s axis, the correct procedure is to align the pole to be parallel to the refracted axis of the pole and this is again a small correction needed to the mechanical alignment of the telescope .The elevation of the refracted pole above the horizon depends upon the declination of the stars being used at that time, so for a complicated and precision instrument, the pole axis should be adjusted for the declination of the object being observed. This complication is beyond the mechanical and technical ability of instruments of the size of the system at the UWS Observatory and therefore corrections need to be made to both axes for the declination dependence of the elevation of the polar axis. A case can be cited where the mechanical elevation of the polar axis of the telescope is adjusted for the declination of the object being observed. The 1.2 m U.K. Schmidt Telescope at Siding Spring Observatory uses an adjustable pole elevation mechanism. The procedure outlined earlier does result in polar alignment to the refracted pole. Thus, in theory, the polar axis allows for one rotation to counteract the rotation of the earth. In practice both axes need to be adjusted in small angles to allow for effects which are usually beyond the mechanical construction of most instruments. This is why the axes must be fitted with precision encoders and precision driving mechanisms to allow for this change. The pointing of the telescope is limited again to one arc-second and as it is desirable to drive the telescope so that the image on the camera is not blurred, it is necessary to have that precision maintained over the duration of the exposure at better than 1/10th of the blur size on the image. In theory we do need to have the telescope maintain it pointing to 1/10th of an arc-second over the duration of the exposure which could be minutes, or considerably longer. This requires a positive feedback system. This accuracy cannot be achieved without precision electro-mechanical engineering.
17 One mechanism of retaining this accuracy in telescope pointing is to adopt an automatic guiding system (or auto-guider) to maintain the instrument in the exact position. The consequence of using an autoguider is that the telescope no longer needs to track to the earlier precision but it does need to exhibit smooth tracking with any jerks in its motion no greater than 1/10 of an arc-second. With smooth guiding and computer controlled adjustments for errors in the tracking, exposure times of up to one hour can be maintained. Some type of automatic guiding system or auto guider is required to maintain the camera in the exact location. One consequence of this is that the telescope needs to not only track with the precision of 1/10th of an arc second but it also needs to exhibit smooth tracking with no jerks in the tracking larger than 1/10th of an arc second. This brings us back to the step size on the stepping motor. This stepping size is smaller than the seeing disk on the image – smaller than 1/10th of an arc second. There is a momentum property in telescope where even though the telescope is being driven along at 1/3rd arc second per step, the momentum in the telescope will smooth much of that out. The design parameters for the UWS telescope called for a stepper size at the motor of 1.8 deg (or 200 steps per turn). The gearbox ratio plus the 9.6: 1 polar disk roller ratio resulted in a stepper size in the sky of 0.06 arcsec.
1.2.10 COMPUTER CONTROL.
The first serious attempt to automate an astronomical telescope was made in 1955 by Bart J Bok (Bok, 1955). It was used for relatively uncomplicated photometry work in the provision of standards for photographic plates (Reddish 1966) and the study of variable stars (Maran 1967). The aim of this early device was to automate the photometric process which collected light from a star, amplified it via a photomultiplier tube and measured it. Several similar systems quickly followed the work of Reddish and Maran and in the early 80’s Martin and Hartly extended the concept by remotely controlling a computerised telescope from a remote computer over a telephone line (Martin and Hartly 1985). The early 90’s saw the emergence of the first effective
18 robotic telescope at the University of Bradford UK (Baruch 1992). This facility was funded by the UK Particle Physics and Astronomy Research Council and the principal aim was to establish the validity of the observing requirements of robotic telescopes as laid down by the UK professional astronomical community. The system was inaugurated in December 1993. The time of this facility coincided with the commercial availability of the cooled CCD camera, and the marriage of these two technologies, coupled with the availability of low cost, powerful PC’s, fostered a growth both in numbers of robotic telescopes and their level of sophistication. The UWS telescope benefited from these developments.
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CHAPTER 2. - MECHANICAL RESONANT FREQUENCIES
2.1 RESONANT FREQUENCIES
Before commencement of the design of the stepper motor drives and the associated gearing, consideration was given to the possible interaction between electronic drive pulses and the mechanical resonant frequency of the various components in the telescope support structure. Indeed, each separate mechanical component would have a fundamental resonant frequency, with the probability of several harmonics. Given that there are two major mechanical assemblies to the telescope, each comprising several sub sections, a large number of resonant frequencies were predicted, each having its associated harmonics. It was thus necessary to establish what these resonant frequencies were and ensure that none of the standard tracking drive pulse rates was selected at those resonant frequencies.
2.2 METHOD USED
A simple method was used to determine the relative amplitudes and position in the spectrum of these frequencies. A vibration sensor was attached to the section of the telescope selected to be under test. A calibrated impulse was applied to that section via a small hammer mounted to act as a pendulum. The energy imparted to each test point could be assumed to be relatively constant by releasing the pendulum from a fixed height. This was achieved by using a small electric magnet at the holding point at the top of the swing and to avoid a secondary “bounce “impulse, a second electro magnet was positioned towards the end of the pendulum swing and timed to activate during the return swing of the pendulum, thus catching and holding the hammer. The output of the vibration sensor was fed to a MacLab console which recorded the peaks of resonant frequency and harmonics.
20 This procedure was repeated on the main sections and sub-sections of the telescope and the combined results are shown in the figure below.
Relative Amplitude
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 (Khz) Frequency
fig 13.Relative amplitudes of the telescopes resonance frequencies.
It can be seen from the above plot that the resonant frequencies ranged from about 100 Hz to 2.1 KHz. More importantly, the spacing of these resonant frequencies was approximately even across the band, and these ‘gaps’ allowed considerable freedom in selecting suitable drive pulse frequencies.
The initial drive train used a reduction gear box with a ratio of 11050:1 and the stepper motor had a 1.8 deg. step angle. The polar axis rotation time was 23 h 56 m 04.1 s. Roller rotation therefore was 147.25 m/turn, input into the gear box was 0.79956 s/turn, thus the stepper frequency was calculated to be 250.1 Hz. It can be seen from the above plot that this drive frequency fits neatly between the first and second resonant frequencies.
21 CHAPTER 3. - ALIGNING THE EQUATORIAL HEAD
3.1 CRITERION FOR LONG EXPOSURE
A substantial quantity of the research work to be carried out at the UWS Telescope will depend on the results of long exposure astro-photography or photo-electric and CCD photometry. The essential criterion for long exposure techniques is that the image remains stationary in the field of view of the measuring device for the duration of the exposure.
Two variables determine the accuracy with which this criterion is maintained: (a.) the tracking rate of the R.A. drive, and: (b) equatorial alignment. For equatorial alignment to be ideal, the polar axis of the telescope must be coincident with the celestial axis, and the declination axis must be perpendicular to the polar axis. An approximate alignment was attained during the telescope’s manufacture and installation. During fabrication care was taken to ensure that the polar axis was angled as close to 33.75 degrees to the horizontal as was possible. The latitude of the UWS Observatory site is 33 degrees 45.725 minutes South. The UWS telescope mounting is a tripod configuration with one mounting foot at the Northern end and two adjustable mounting feet at the southern end, one to the East and one to the West. Vertical adjusting screws are fitted to each foot to allow fine adjustment of the height of each mounting point individually. Furthermore, east-west movement of the Southern end of the telescope is accommodated by horizontal adjusting screws in the east/west direction. The permanent retaining bolts are fitted into slots which when tightened hold the telescope in permanent position once the alignment is complete.
3.2 ALIGNMENT METHOD The Astronomy Department of UWS had purchased some black and white CCTV equipment primarily for use in demonstrations of the facility to the general public,
22 school groups, etc. It was decided to use part of the TV equipment in the alignment process. The apparatus consisted of;
a) a 17” monochrome TV monitor b) a monochrome 1/3 inch CCD TV camera c) a Tektronix TV pattern generator type TSG 95. To eliminate errors in the TV system due to scan non-linearity and scan rotation in the TV monitor, a cross hatch pattern from the TSG 95 pattern generator was displayed on the 17” monitor and a copy of this pattern was traced on to the front glass of the picture tube using a thin felt tipped pen.
fig 14. Eliminating non linear scan error using an electronic pattern generator
As well as eliminating any scan errors in the monitor, the traced graticule provided an accurate scale to measure drift because the electronically generated video lines were
23 separated by the exact number of TV scan lines. The vertical scan circuitry of the monitor was modified to increase the vertical scan by approximately 50% to further increase the scale and therefore the reading accuracy of the graticule. The CCD camera was attached to the telescope eye piece and its output fed to the 17” monitor. Note: It became clear during the subsequent alignment procedure that significant parallax errors could be introduced into the measurements because of the thickness of the front glass of the CRT i.e. the image created on the phosphor of the tube was displaced approximately 10 mm behind the cross hatch trace on the front of the glass. This could have been eliminated if the pattern generator had been genlocked to the CCD camera, and the two video sources mixed or keyed up stream of the monitor. As a genlock facility was not available on the Tektronix TSG 95 particular care had to be taken to avoid these parallax errors. Using a spirit level and the east/west height adjusting screws, the southern end of the telescope was made to be approximately horizontal as a basic starting point.
3.3 ALTITUDE ADJUSTMENT To align the CCD camera’s rotational position a bright star at the zenith was positioned in the vertical centre of the picture and the sidereal drive turned off. As the star tracked across the field of view the camera was rotated until the trajectory of the star was parallel to the horizontal graticule on the monitor. Monitoring the movement of the star relative to the fixed graticule became the basis of measurement. The geometry of the alignment of a telescope is as follows. A star is selected in the east and another in the west. Both stars should be at least 5 hours from the meridian and at a declination of about 45 degrees south. Positioning each star in turn on the centre of the monitor graticule and with the sidereal drive turned on, a movement due to misalignment will be noted in a north/south direction. If the east star drifts north and the west star drifts south the elevation of the south end of the telescope is too small. Conversely, if the east star drifts south and the west star drifts north the elevation of the south end of the telescope is too great.
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The table below shows the adjustment increments made and the resultant alignment error.
Meas. No Duration Star Error Direction Adj Dir Adj Size Mins 1 6 E 45 N S down 4.7 mm 2 6 W 22 S S down 1.2 mm 3 6 E 18 N S down 2.6 mm 4 6 W 5 N S up 0.6 mm 5 10 E 2 S S up 0.8 mm 6 10 W 2 S S down 0.2 mm 7 10 E 1 N S down 0.1 mm 8 10 W 0.5 N S up -- 9 10 E 0.5 S S down -- 10 15 E < 0.5 -- --
fig 15. Elevation adjustments and resulting error
Note – Error units are numbers of pairs of TV scan lines. Adjustment magnitude units are based on degrees of rotation and thread pitch of the adjusting bolt.
25 3.4 AZIMUTH ADJUSTMENT.
The technique used for azimuth adjustment was similar to that used for altitude alignment. A star was chosen near the Meridian and close to the celestial equator. The applying geometry states that if the star drifts north then the azimuth error is towards the NW-SE direction. i.e. the southern end of the polar axis is pointing east of south. The following table shows the increments of azimuth adjustment and the resulting error.
Meas No Duration Error Direction Adj Dir Adj size 1 5 37 North West 10 mm 2 5 22 North West 6.5 mm 3 5 12 North West 5.5 mm 4 5 4 South East 5 mm 5 10 2 North West 2 mm 6 10 1 South East 1 mm 7 10 1 North West 0.7 mm 8 10 1 South East 0.3 mm 9 20 1 South -- 0.1 10 20 < 0.5
fig. 15.1. Increments in azimuth and the resulting error.
26 At the completion of this alignment procedure, zero drift could be measured over a 20 minute viewing session with the resolution of the equipment used. A non- interlaced or a 100Hz frame rate TV system may have improved this resolution.
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CHAPTER 4. - INITIAL TRACKING AND SLEWING CONTROL SYSTEM
4.1 TRACKING AND SLEWING SYSTEM
To allow students and the viewing public an opportunity to make use of the UWS Telescope during the construction period of the computer controlled robotic system an interim tracking and slewing drive system was installed. It proved to be an economical and reliable solution and its tracking accuracy was sufficient for general applications, however, not sufficiently accurate for long exposure measurements. It consisted of a variable frequency oscillator driving a proprietary stepper motor controller (RCC type SMD-1) which in turn drove a Vextra 1.8 degree per step motor through a 11,050:1 gearbox on to the 9.6:1 Polar disc drive. The 1.8 degree per step motor through the above gear reductions produced a step size in the sky of 0.06 arc sec. Further, a stepping frequency of 250.1 Hz was calculated to produce the correct tracking rate. A stepping frequency of around 6 KHz would give a workable slew rate. The same variable frequency oscillator and stepper drive was used for the focus stepper motor on the secondary mirror mount. A bank of relays switched the drive outputs from the stepper driver to each motor. The following diagram shows the circuit of the variable frequency oscillator.
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fig 16. VFO Circuit Diagram
A potentiometer was mounted on the hand paddle to provide a variable voltage input to the variable frequency oscillator (VFO) which enabled varying stepper rates for both HA and DEC. The potentiometer was of the type fitted with a push-pull switch action on the shaft and this switch was used to change the VFO input from the hand paddle potentiometer to an internally mounted multi turn trim potentiometer which was adjusted to provide optimum tracking pulse rate. A small hole in the side of the hand paddle gave access for screw driver adjustment of this potentiometer as would possibly be required from time to time.
Switches were mounted on the top edge of the hand paddle to switch the output of the stepper motor controller to any one of the three stepper motors in the system. Pointing to a star that therefore required sequential and repetitive actions in both HA and DEC.
29 Once the target was centred, the focus motor could be individually activated. However, because the tracking motor could not operate simultaneously with the focus drive motor, any focus adjustments needed to be done quickly as the star moved across the field of view. Considerable operator practice was needed before the technique could be mastered. The operating sequence was: a. Move HA axis to the approximate pointing position b. Move DEC axis to the approximate pointing position c. Fine tune HA axis for object centre d. Fine tune DEC axis for object centre e. Check/adjust focus f. Repeat c and d g. Push control knob to invoke VFO tracking rate h. View
The figure below shows the original hand paddle.
fig 16.1 Original system hand paddle
30 CHAPTER 5. - THE VIDEO SYSTEM AT THE UWS OBSERVATORY
5.1 TASKS The video system at UWS was required to perform several tasks covering research, on site education, public viewing, and remote viewing through the Hands on Universe program.
5.2 ON SITE EDUCATION. The UWS Nepean Observatory has a small lecture theatre attached to the main telescope building. Several courses are offered by the astronomy group ranging from Undergraduate Degree courses to advanced Masters and Doctorate degrees. In conjunction with the formal courses offered by the University, school groups are invited to attend lectures and demonstrations as an aid to their high school science courses as well as fostering a greater interest in science, and astronomy in particular. It was clear that most, if not all, of the imaging devices needed to be displayed on all the large screen colour TV receivers as well as the large screen TV projector mounted in the Observatory’s lecture theatre. A system of U.H.F. distribution was selected over base band video to reduce cabling and installation costs and to free the lecturer to select any required channel from any position in the lecture hall via a standard infra red remote control. Base band video distribution would have increased the cost of the installation due to the need for a quantity of video distribution amplifiers and extra cabling, but would also have made it necessary for the lecturer to be at a fixed point in the lecture theatre i.e. at a switching panel, to select the required video source to be displayed. An added advantage of R.F. distribution was that the multi-channel signal could be sent to other buildings on campus either by coax cable or via microwave link. The initial video system included 10 video sources, and as it was highly probable that other sources would be added in the future, the system design
31 needed to allow for easy integration of additional video facilities. A multi input electronic routing switcher would have provided an ideal heart for an expandable system, but as budgetary constraints prohibited this approach, a passive video patch panel was constructed.(See later comments on the desired router, page 42).
fig 17. Video patch panel.
32 Initial sources were as follows: a) 1/3 inch monochrome high resolution CCD camera mounted on the instrument turret. b) 1/3 inch monochrome CCD camera mounted on the C8 telescope. c) 1/3 inch colour CCD camera designated “Moon cam”. d) 1/3 inch monochrome CCD camera floating. e) ST 6 video capture. f) ST 8 video capture. g) 1/3 inch monochrome CCD camera showing a wide angle view of the inside of the dome. h) Cuseeme colour camera mounted at the operators’ desk for internet display. i) 1/3 inch colour CCD camera mounted outside the dome designated “Cloud cam”. j) VHS video recorder.
The principal camera for the telescope is a Santa Barbara Instruments Group (SBIG) ST8 integrating CCD camera. This camera is based on a Kodak 1600 chip which has 1.5k pixels x 1k pixels, each pixel being 9 microns in size. In addition to the principal chip inside the camera there are smaller chips which are designed to pick up the off axis star images, and to centre these images at very fast frame rates and to feed back to the telescope drive to ensure the telescope is in fact tracking the stars as they go. This eliminates many of the problems referred to above in terms of refraction and polar alignment. Experience with this camera has shown that the images of stars as faint as 19th or 20th magnitude can be obtained in exposures of 5 to 10 minutes which makes the camera and this telescope combination a very competitive tool in terms of many areas of science, principally astrometry and photometry. The images captured by this camera are analysed on a dedicated computer which is called the “camera computer” using the software which is supplied with the camera (called CCDOPS), or alternatively the maxim DL software which was purchased after the installation of the camera. The image from this camera and from this computer monitor can then be distributed either to
33 the internet or alternatively other parts of the building, in particular to the TV monitor and data projector in the lecture theatre. The other cameras on the telescope are designed to piggyback on the main camera and on the main instrument. In particular there is an 8” Celestron telescope mounted parallel to the main instrument with a black and white video frame rate surveillance type camera inserted into the eye piece. This instrument is particularly sensitive to Luna features and gives a very satisfactory view of the moon in less detail than the main camera but gives a frame rate so atmospheric change and tracking changes of the telescope etc can be seen. In addition there is a colour wide angle lens arrangement on the side of the telescope designed to give a full view of the moon. The field of view is approximately 45 arc minutes in the vertical and this gives a full view of the moon and is ideally suited for the entertainment and education of younger people who identify very clearly with the moon as part of their studies. This camera when fitted with a solar filter also gives a full frame view of the sun and has been used for web broadcasts of partial solar eclipses seen over Penrith.
We refer to this camera as the “moon camera” and it consists of a 1/3 inch CCD surveillance style colour camera fitted with a 300mm telephoto lens. This combination gives an ideal field of view of about 1 degree x 45 arc minutes. It was the intention to fit 2 other cameras to the main telescope, one of these was to be an ST6 integrating, cooled CCD camera (of less power than the principal ST8) which was to carry a wide angle camera lens for viewing of wide angles of the sky. This camera was to be mounted at the top of the telescope. In addition there was also to be a frame rate video camera of high sensitivity mounted at the top as a “constellation camera”. As well as cameras on the telescope there is a small CCD surveillance camera mounted inside the dome which shows images of the telescope and people in the dome.
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fig 18. Moon cam mounted on the side of the main frame
35 Irrespective of the number of video pictures being generated within the university, consultation with the lecturers indicated that no more than five different sources would be required during any one lecture period. With this in mind, a five channel U.H.F. TV modulator system was installed utilising channels 43, 45, 47, 49 and 51. The channels chosen were somewhat at random whilst having regard for potential interference from high power U.H.F. transmitters already operating in the Sydney basin, mostly commercial and community access TV channels. While restricting the total of U.H.F. channels to five, provision was made to quickly change any of the U.H.F. modulator inputs via the video patch panel so that any of the modulators could be connected to any of the video sources at any time. See the video schematic diagram for further detail.
fig 19. Rear view of the UHF modulators
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5.3 REMOTE VIEWING
Two avenues for remote viewing were considered. i) The Web Page: Within a week of completing the video switching and distribution system, UWS had an opportunity to display the images of a solar eclipse on the UWS home page on Tuesday 16th February, 1999. In preparation for the eclipse a 1/3 inch colour CCD camera was mounted on the side of the main telescope and was fitted with a 500 mm lens with an ND solar filter. The camera utilised a 1/3” colour CCD with 512 horizontal x 582 vertical pixels (9.6 micro m horizontal pitch). During the eclipse the images were recorded on a VHS tape recorder and were displayed on colour monitors throughout the Observatory. To facilitate remote viewers the image was displayed on the university web page using the following technology. A video capture device (Video Blaster I.E. 500) was used in conjunction with the software package “Image Pals Image Editor” and saved in jpeg format. This was uploaded to Web server-bacall.nepean.uws.edu.au using wsftp.exe. This process was to be fully automated but due to software conflict between SNAP+send and Video Blaster drivers, the capture and upload sequence was performed manually every 45 seconds. This software conflict has since been rectified and real time images are now available to the net. Feedback on the educational value and the extraordinary interest shown in this home page imaging is discussed later in this document. ii). The results of a questionnaire distributed to lecturers and potential remote users, was evident that whichever video source was currently being displayed on the web page, should be that which is being displayed on the Cuseeme overlay on the main telescope display screen.
37 The video sources available to the remote viewer were more numerous than those likely to be used in any one lecture session or indeed in a lecture room environment. For example, apart from the normal instrument mounted cameras, images needed by remote viewer could include:
• CLOUD-CAM. The outdoor colour CCD camera mounted on a remotely controlled pan and tilt unit to allow remote users to check during late afternoon the likelihood of evening cloud.
• The Cuseeme CCD colour camera to enable real time, face to face conferencing.
• The view of the main telescope from inside the dome to show telescope type, mechanical features, movement etc.
5.4 REMOTE SCIENCE
This area of remote viewing was required to fulfil the needs of a range of users with vastly different levels of astronomical knowledge and scientific requirements. In spite of this, it seemed probable that any of the available video sources could be called upon at some time by any of the potential users. In most cases the required image would be needed to be displayed as an overlay on the control panel screen, and in applications requiring better definition, stored and dispatched via email at a later time. The latter approach would be more appropriate for instance following a long duration data gathering exercise using the ST8. These images, plus other sources commonly used in house needed to be remotely selected by the remote viewer/operator as well as being selected locally. To achieve this dual role, an inexpensive remotely controlled 10 input vision switcher was purchased (M.C. Corporation model YH438C). This vision switcher not only enabled switching of individual inputs to a selected output but also provided 2 quad images as outputs. The first quad selection combined cameras 1 through 4 in a quad format, and the second gave cameras 5 through 8
38 in quad. In total any one of 10 outputs could be selected being cameras 1 through 8, quad A, quad B. The remote control of the YH438C is via a high density 15 pin D connector requiring 6 logic control lines (see the video schematic diagram for details page X), and was driven by the ACE control system.
fig 20. YH438C Quad video switcher ( smart dome control unit below)
5.5 RESEARCH.
The principal video research tools available to UWS were a large format ST8 CCD integrating camera (by Santa Barbara Instrument Group) and two ST6 integrating cameras. The images from these cameras were required to be available at several destinations being: i) the UWS Observatory image library ii) remote users via the Internet
39 iii) public viewing monitors within the Observatory iv) on site lecture theatre monitors and large screen projectors. Video capture cards were used in the camera PC so that both digital and composite video signals were available for distribution.
5.6 PUBLIC VIEWING
Due to the limited size of UWS observatory facility, public viewing times needed to be scheduled outside of formal lecture periods. This physical restriction freed the lecture theatre UHF distribution system for public viewing use. However, further public viewing facilities needed to be added to the upper level of the observatory adjacent to the main telescope. Two TV monitors were placed adjacent to the telescope, and input selection of any of the sources was made available to these monitors by passive rotary switch banks. Two monitors were chosen to enable the image from the main telescope to be displayed along side a wider view from the three inch or C8 telescopes.
The video system as described above is probably as flexible a system as could be managed under the given budget constraints. Unfortunately it became clear that because of the system complexity, appropriate training had to be given to those faculty members who were likely to have specific and different demands on the system. A common question being “How do I configure the system to get it to do what I want ?” Instruction was given to each operator on how to change the system from its standard/default configuration to the required configuration for his/her session. After some weeks of multiple usage it became clear that more work was necessary to simplify the operational controls and to simplify the method of setting the system to a varied number of standard configurations. The main problems were introduced through operators not returning the configuration to the default condition after use. This meant that the next operator would input his requirements assuming he was starting from a default setting, and finding that the end result was not as expected and certainly not as required. Two solutions were considered.
40 a. A colour coded default finder. The original method of setting the system to its default configuration was to refer to the system block diagram mounted on the equipment rack in the computer room. Reading this block diagram and initiating the required changes proved to be a more difficult task for most operators than had been expected. To overcome the need to refer to the block diagram, a colour code system was introduced whereby mating connectors on the patch panel, switch positions etc. were colour coded to a standard format e.g. connecting the red patch cable to the red patch connector and/or switching to blue along the chain quickly attained default conditions. From here, each operator could then modify the setup to provide his/her standard configuration for the next session. Reference to the block diagram would still need to be made where a non standard configuration was required or if any changes needed to be made to an existing standard. These changes proved to be a regular occurrence, but the colour code system again was a great help in returning the system to default. b. The need for a microprocessor controlled video routing system. Most of the problems, queries and out time that occurred in operating the video system were through operator error. This was due to either unfamiliarisation with the system or requesting the system to perform a task that it was not designed to do. Removing the human element from the back ground operations of system setup seemed appropriate and a microprocessor controlled video routing switcher seemed the best solution. Several commercially available systems were investigated, all being of matrix configuration made up of 16 inputs and into 16 outputs .Parameters such as frequency response, video path cross talk, distortion, control panel configurations, power consumption and ease of maintenance were compared. A most important operational feature in the considerations was the ability of the system to perform what are known as “salvo takes”. This feature permits a number of standard matrix configurations to be
41 stored in memory and activated at will by one or two key strokes. This feature seemed mandatory for UWS facility in that each operator could be allocated a dedicated matrix configuration number which would be entered at the start of that operator’s sessions. If a public viewing session is taken as an example the optimum system configuration could be manually entered into the processor and allocated salvo take “one”. The salvo take facility then allowed all public view sessions in the future to be configured by one or two key strokes from the supervisor. Once this was established any modifications to the standard matrix configuration could be carried out by direct switch action into the matrix. After considering the requirements a short list of two quite different systems resulted. These were; i) A matrix fully self contained in a 19” rack mount cabinet with both local and remote controls, and redundant power supplies manufactured in Australia by Talia Video. The Talia systems are aimed at the broadcast and semi professional video production market. As such, the video performance specifications met or exceeded the requirements of the UWS facility. Moreover, provision could be made for easy system expansion if required some time in the future.
ii) A matrix system manufactured in the USA by Javalin Inc. The Javalin system is supplied in kit form for assembly into a desktop personal computer. Neither local nor remote switch operated control panels are available as all matrix configurations are done via the PC screen. Performance specifications of the Javalin system were not as rigid as the Talia device but were considered adequate for the UWS facility. The major limitation with the Javalin system was the inability to provide individual local or remote switch panels. At the time of writing, budgeting considerations prohibited the purchase of either of the above video routing systems and as a result, the colour coded manual system is currently in use. See chapter headed “Future work to be carried out” in chapter 9 for further details. The next page shows the video schematic diagram of the UWS TV system.
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fig 21. Video schematic diagram
43 5.7 A NOTE ON GAMMA CORRECTION
If the early days of television development had started with the technology of liquid crystal or plasma displays, the concept of gamma correction would never have been an engineering issue. Alas, cathode ray tubes (CRT) were the first display devices and as such the TV industry is burdened with a forced, built in distortion of the television image which needs to be corrected later in the processing chain.
The cathode ray tube was invented by Karl Ferdinand Braun in 1897. It is constructed of an evacuated glass envelope with a Phosphor-coated screen at one end which emits light when hit by electrons generated by a heated cathode. These electrons are focused into a beam and forced to scan the phosphor screen by a process of magnetic deflection. The intensity of the electrons hitting the screen, and therefore the intensity of the light output is varied by modulating it with a control grid in the electron gun.
It was soon discovered that the intensity of the light output of the CRT screen was not proportional to the intensity of the electrons being emitted by the electron gun. More specifically, the light intensity in the dark (grey) areas of the picture was less than the proportional amount of electrons would be expected to create. i.e. the dark areas were being crushed into the black.
This distortion clearly needed to be corrected and extra gain was needed to be added to the grey, and more so in the dark grey, areas of the picture. Extra gain equates to extra noise in the video signal and unfortunately the human eye is more sensitive to noise in the dark areas of a picture than in the brighter areas. The electronic circuits to produce this extra, non-linear gain therefore needed to be designed with optimum performance and greater complexity.
It seemed obvious at this stage that the number of television cameras in use at any one time would be vastly outnumbered by the number of television monitors and receivers, so a decision was made on economic grounds (by the engineering fraternity) to include this extra non-linear gain in all cameras, rather than in each CRT display device. A
44 “pre-correction” if you will. The commonly accepted value of gamma in today’s TV cameras is 0.5 i.e. the voltage output of the video signal is raised to the power of 0.5. The diagram below shows the relative curves and the resultant linear output.
fig 22. Gamma Correction curves.
LCD and plasma displays show a linear transfer characteristic (i.e. voltage input is directly proportional to light output). However, because all cameras still need to accommodate CRT displays, and thus the signal is gamma pre-corrected, a “de-gamma” circuit must be incorporated in the LCD type displays. It is assumed that CRT devices will eventually be phased out but it is difficult to imagine how and when a removal of gamma correction could take place because the overlaps in technology will demand that correction or de-correction is necessary to cater for all existing devices.
The relevance of gamma in TV astronomy is that most of the viewing of celestial objects displays scenes of a black background, with white objects in the foreground. i.e. very few or no grey areas. Moreover, if grey areas are present they are often unwanted aberrations. The exception to this rule would be in viewing craters of the moon where grey areas exist and in most cases are required to be replicated in the viewed image.
45 Consequently using conventional gamma corrected cameras in TV astronomy introduces an unnecessary “black stretch” in the video path and the noise in black that it, by definition, enhances. An added desirable feature therefore, when selecting a television camera for astronomy use is an external gamma control, at its simplest “gamma ON/OFF”. Using such a feature can minimise thermal noise in the black areas of the picture thus enhancing the effect of the overall image. Due to budgetary constraints, the only camera fitted with adjustable gamma was the one mounted on the instrument turret.
fig 22.1 1/3” CCD camera with adjustable gamma
46 5.8 STAR-TRAK
In the earlier chapter covering mechanical alignment of the telescope, a description is given of the closed circuit television operation to aid in the measurement of system drift. During this alignment procedure it became clear that errors due to parallax could readily be introduced, or at the very best, that extra time and care had to be spent in making sure that parallax errors were minimised. With this in mind a software application called Star-Trak was developed. As the design goals of Star-Trak were prepared, its application to other areas of astronomy became clear and a far more useful research tool resulted.
To avoid parallax errors when using a cathode ray tube for measurements, the image being viewed by the CCD camera must be mixed electronically with the reference graticule prior to display. The technically correct method to perform such a mix is to KEY the foreground video (i.e. the graticule) into the background video (i.e. the star scene being viewed). To perform a key function, a “hole” is cut into the background video in the size and shape of the required foreground. This hole is then filled with another video source, in our case 100% peak white. This key method allows for a variable grey scale to be used as the fill signal which, while not defined at the time of development, was seen to be a possible use in the future. The alternative to key technology was an additive mix approach which although electronically easier to implement has the disadvantage that the live video sources are added over the entire frame resulting in loss of grey scale integrity. To achieve a stable keyed picture, the scan rates of the two video sources need to be synchronised and locked horizontally and vertically, or “genlocked”. Several proprietary PCB’s were commercially available which provided most of the required genlock and key functions. The one chosen by UWS was the system manufactured by Cueword Pty Ltd in Sydney. The Cueword system was developed for use by TV stations for teleprompting scripts and open captions for on-air presentation. The benefit of the Cueword system was that it provided an onboard genlock and key function which were intended to output onscreen captions for the hearing impaired. So, the celestial image could replace the “talent” image and the graticule would replace the captions. All that was needed now was a software package which would generate a suitable graticule.
47 Clearly a rigid, non moveable graticule was required as a reference for measuring image drift, and a suitable solution was a cross hair in the centre of the television raster. With a view to future experimental work, a second mouse-moveable cross hair was provided which could be moved to any part of the TV raster. The reason for the development of the moveable cross hair was that it could be used for the following task. a. An auto “go to” function. Operationally the auto go to function required the moveable cross hair to be moved to the stellar object under study. A click on the mouse would then instruct the software to determine how many pixels both horizontally and vertically the moveable cross hair was displaced from the fixed cross hair at the centre of the raster. A new reference could then be calculated either by Star Trak, and the telescope would move to that new position automatically. b. Measuring angular distance between stars. By placing the fixed cross hair on one star, and placing the moveable cross hair on another star, the known angular separation between the two stars could be used to perform an auto calibrate function. From then on, a digital readout on the CRT would give the angular separation between the centre cross hair and any other position within the raster that the moveable cross hair was placed. c. As a teaching aid. The moveable cross hair could be used as an electronic pointer during lectures, tutorials and public viewing.
5.9 PRECAUTIONARY NOTE.
Many CCD cameras of the type used in astronomy are chosen for reasons of high sensitivity, low noise, adjustable gamma and stability of gain and scan frequency. Under normal circumstances the tolerance of scan frequency stability is of little consequence because the average TV display monitor is designed to accept a broad range of scan frequencies to accommodate multiple standards, noisy sources and poor synchronizing pulse trains from video cassette recorders. Horizontal scan frequency and
48 stability are of increased importance when dealing with genlockable equipment. Not only should the nominal horizontal centre frequency be within 2 Hz of the specified standard, but drift, mainly due to temperature changes, should be less than a further 1 Hz. This is because the sync pulse detector and separation circuitry of the average genlock system is far less forgiving than a standard TV monitor.
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CHAPTER 6. - ENGINEERING APPROACHES TO TELESCOPE AUTOMATION
6.1 GO-TO
The basic requirement of a telescope automation system is to have the device ‘Go-To’ a specified target and accurately track that target as it moves across the sky.
Several levels of engineering can be employed in achieving the above goal. Cost is the most common factor in determining the level of sophistication of the control mechanism. The more sophisticated and thus more expensive levels giving greater accuracy compared to the less expensive, more basic models. Furthermore there are two fundamentally different engineering concepts on which to build a Go-To control system.
Firstly, an open loop system of electronic control where a drive system responds to instructions given by an operator from a keyboard or hand paddle. In an open loop system, no positive feedback is given to the drive system control to give confirmation that the required action has taken place with accuracy, or indeed if the action has taken place at all. Furthermore, if the telescope is moved manually (e.g. n degrees in DEC) the drive system has no means of recording this change and so believes that the telescope is still pointing to its pre manually moved position. The end result of this is that when a new Go-To instruction is given, the system uses an invalid starting point and drives the telescope to a new position which will be ‘n’ degrees in DEC off the required target.
To overcome this problem, many telescopes using open loop systems eliminate the possibility of performing a manual move so that the electronic drive system becomes the only means of movement and therefore can maintain constant position surveillance
50 integrity. This of course leads to rendering the instrument useless if a failure of power supply or a fault in the drive system occurs. The first drive system at UWS, described earlier, was an open loop system, however manual override was maintained.
Secondly, the much preferred closed loop system may be used where components (usually optical encoders or precision potentiometers) are mounted on the telescope drive train to provide a constant feedback to the control electronics of any movements whether manual or automated. Consequently if the telescope is moved the control system will know where the device has been moved to and thus does not lose its orientation.
The precision with which these devices can deliver the feedback information to the control electronics is paramount in determining the accuracy with which the telescope will ultimately point and track. The key parameters in attaining this precision are: The resolution of the encoder Minimising backlash in coupling devices Slippage between friction drive rollers Ability to accommodate slight off-axis mounting.
Optical encoders, or shaft encoders, monitor the direction of rotation and the distance travelled. Two encoders are usually employed on an astronomical telescope, one for feedback of movement in the Declination and the other in Right Ascension. The direction information is usually supplied via one pair of conductors and the step counts, or ‘TICS’ via another pair. Careful consideration needs to be given to proper earthing and shielding techniques during installation because stray TICS entering the feedback loop via external noise or power supply spikes will corrupt the final count at the processor end of the chain. An alternative to the optical encoder feedback system is a d.c. servo controlled system. The feedback device in this application is usually a precision multi-turn linear curve potentiometer. The position of the moving arm of the
51 potentiometer, and thus the resistance or voltage output is a direct reflection of the position of the telescope.
The gearing used to couple the multi-turn potentiometer to the telescope must be carefully chosen so that the maximum angular movement of the axis concerned does not exceed the end-stop to end-stop length of the potentiometer’s conductive track. This usually calls for a high gear ratio, using a chain of gears, which is in turn conducive to the introduction of increased backlash. The limiting linearity of the track of even the best potentiometers, plus the mechanical problems introduced via a complex gear train usually relegate the d.c. servo system to a less expensive telescope drive system. The slight extra cost of a servo motor verses a stepper motor is more than offset by the lesser cost of the feedback sensor. A summary of the benefits and drawbacks of stepper and servo motors is given below.
6.2 STEPPER MOTOR BENEFITS
• Rugged and reliable. Steppers are mechanically very simple and apart from the bearings no wearing components exist.
• Lowest cost solution. • No maintenance. There are no brushes or other wearing parts requiring regular checking or replacement.
• Industry-standard ranges (Nema or metric). Steppers are produced to standard flange and shaft sizes so finding alternate sources is not a problem.
• Inherently failsafe. There are no conceivable faults within the drive to cause the motor to run away. Since current must be continually switched for continuous rotation most faults cause the motor to stop rotating. A brush motor is internally-commutated and can run away if continuous current is applied. A brushless servo relies on the feedback signal. If the feedback signal is damaged or absent the motor can run away.
• Not easily demagnetised by excessive current. Owing to the perpendicular planes of the permanent magnet and alternating flux paths, stepper motors will
52 more often melt the windings before demagnetising the permanent magnet as would happen in a brushed motor.
• Inherently stable at standstill. With DC flowing in the winding, the rotor will remain stationary. There is no tendency to jitter around an encoder position. This is useful in applications using vision systems.
• Can be stalled indefinitely without damage. There is no increase in motor current as a result of a stall as in a servo system. There is no risk of overdriving a stepper system due to large loads.
• High continuous torque in relation to size. Compared with brushed servos of the same size, a stepper can produce greater continuous torque at low speeds.
6.3 STEPPER MOTOR DRAWBACKS
• Ringing resonance and poor low speed smoothness. These are criticisms generally levelled at full-step drives. These problems may be almost wholly overcome by the use of a high resolution drive.
• Uses full current at standstill. Since current is needed to produce holding torque, this increases motor heating at standstill.
• Noisy at high speeds. The 50 pole rotor has a magnetic frequency of 2.5 kHz at 3000 rpm. Magneto-striction causes a correspondingly high pitched sound.
• Excessive iron losses at high speed. Again due to the high pole current, hysteresis and eddy current losses are higher than in a servo. A stepper is therefore not recommended for continuous operation at speeds above 2000 rpm.
6.4 BRUSH SERVO BENEFITS
• Low cost. Brush servo motors are well developed and are inexpensive to produce.
• Smooth rotation at low speeds. Brush motors are available which are specially designed for low speed smoothness with a large number of commutator
53 segments. Brushed motors are the smoothest of the three discussed motor technologies.
• Low cost electric drive. A dc brush drive can be made very economically since only a single bridge circuit is required.
• No power used at standstill. With no static loads on the motor no current is required to hold position.
• High peak torque availability. In intermittent duty applications, particularly when positioning mainly inertial loads, the motor can be overdriven beyond its stated continuous rating.
• Flat speed/torque curve. This provides optimum performance with easily generated linear acceleration ramps.
• High speed attainability. Brush servos are typically good for speeds up to 5000 rpm.
6.5 BRUSH SERVO DRAWBACKS
• Brush maintenance. This is not necessarily a problem if the motor is easily accessible, but a nuisance if the motor is not. Brushes also create dust as they wear, thus limiting their use in environments where brush dust is not acceptable.
• Commutator limitations. Arduous duty cycles promote wear, and the mechanical commutation limits top speed. Very short repetitive moves less than 1 revolution of the motor may wear part of the commutator.
• Poor thermal performance. All the heat is generator in the rotor, from which the thermal path to the outer casing is very inefficient.
• Can be demagnetised. Excessive current can result in demagnetisation of the motor.
6.6 BRUSHLESS SERVO BENEFITS
• Virtually maintenance free. The lack of a commutator and brush system eliminates the need for periodic maintenance.
54 • Good thermal performance. All the heat is generated in the stator where it can be efficiently coupled to the outside casing.
• Very high speeds possible. There is no mechanical commutator to impose a speed limit, small motors are typically rated at up to 12000 rpm.
6.7 BRUSHLESS SERVO DRAWBACKS.
• Higher motor cost. This is largely due to the use of rare earth magnets. • Electric drive more complex and costly. Six state or trapezoidal drives, are not much more expensive than d.c. brush drives, but the higher performance sign wave drive can cost several times that of the d.c. brush drive.
The following chapter (chapter 7) describes the motors and drivers chosen for the UWS system.
55 CHAPTER 7. - THE CONTROL SYSTEM AT UWS
7.1 CHOSEN SYSTEM The system chosen for automated control of the UWS Observatory Telescope was that offered by Astronomical Consultants and Equipment, Inc (A.C.E.) of Tucson, Arizona, USA. It comprises all the necessary hardware and software to automate an equatorial mount telescope. It consists of a PC running Windows NT4 and a proprietary ACE telescope control crate. The system controls the movement of the telescope, the observatory dome rotation and the shutter. It uses an Oregon Micro System PC58-4E digital IO card which is responsible for running the motors, reading the encoders and other external inputs such an end stops, hand paddle, shutter condition etc. It is capable of controlling up to 4 motor/encoder pairs.
The system drives DM/DR series Dynaserve servo motors and reads Dual Quadrature Rotary encoders for the Declination and Hour Angle axes, and stepper motors for the secondary mirror focus adjustment and also for the instrument selector turret. These servo motors are of the brushless variety described in chapter 6 and are able to provide resolutions up to 1,024,000 steps per revolution. They are direct drive devices, using an outer-rotor design, allowing them to be coupled directly to the load without the need for large reduction gearboxes which invariably introduce unwanted backlash.
fig 26 . Outer-rotor construction of the Dynaserv motors (Reproduced from the Dynaserv installation manuall)
56 A second advantage of the outer-rotor construction is the extra torque available. Torque is proportional to the square of the sum of the magnetic flux of the permanent magnets, and the magnetic flux of the stator windings. The outer-rotor design allows the tangential forces of the rotor and the stator to work at a greater distance, thus increasing the output torque. The diagram below shows output torque versus speed.
fig 27. Output torque versus speed of the DM/DR series motors. (Reproduced from the Dynaserv installation manual)
In addition to overseeing the movement of the telescope and dome, the PC monitors inputs from the weather station mounted on the Observatory’s roof and sends drive instructions to the quad video switcher, assigning the required video source to the input of the internet connection.
The interconnections of the ACE system at the UWS Observatory, plus the relevant colour codings are given in the attached extracts from the ACE system handbook given in appendix A.
57 7.2 MAKING THINGS EASY
When mounting the feedback encoders and couplers to the Hour Angle and Declination axes of the telescope, standard proprietary hardware was used wherever possible. However, because of the structure of the base of the rotating dome, a UWS specific device needed to be constructed to mount the encoder which supplied feedback of the dome position to the controlling PC. This was elegantly achieved by using parts from a discarded semi-professional video tape recorder, in this case a Panasonic U- matic. The capstan drive idler wheel, complete with its accompanying frame, bearings etc, proved to be ideal. The idler wheel is a 10 cm diameter cast alloy wheel with a hard rubber tyre fused around the circumference. This hard rubber tyre was designed for use over many hundreds of hours of tape replay so, although thin in profile, the tyre proved to be an excellent, high friction, minimum slip coupler between the metal dome base and the encoder. The eccentricities of the dome’s base were compensated for by mounting the base plate to a vertical pin hinge, and using spring tension to hold the idler wheel against the dome base. If any slippage was to occur, a micro switch and cam system was used as a method of recalibrating the encoder position each time the dome passed its home site. Because of the heavy duty nature of the tyre and the roller bearings on the idler shaft (part of the original U-matic recorder) this device has been operating successfully for over 3 years.
58
fig.28 U-Matic idler wheel coupled to encoder below
7.3 SAFETY
Occupational Health and Safety issues mandated that many personal safety aspects to be considered during the design and construction of the UWS Telescope and Observatory. Safety aspects associated with building codes are outside the scope of this document, however some aspects of personal safety considerations around the telescope are mentioned here.
Because the UWS facility was to be open to school age groups, ranging in age from 10 to 18, consideration needed to be given to ‘small hands in tight places’ in a darkened, often blacked out environment in which a multi tonne device was slewing and tilting at sometimes very high rates. To this end, mechanical aspects such as all sharp edges and any small spaces between adjacent parts of the moving assembly needed to be addressed first. In most instances the sharp edge issue was addressed merely by
59 rounding off all exposed edges of the assembly and the small space issue by fitting cover plates to all openings that were a threat to personal safety.
A further consideration was the electric cabling associated with both the drive motors/encoders, and the TV cameras and other turret mounted instruments. Because the cabling requirements needed to be changed when using different measuring instruments, some cabling needed to be free of the restrictions of hard clamped conduit covering. Conduit, or spiral spring wrap, was used where possible but to cater for ‘one off use’ cables, a series of strategically placed cable clips were mounted on the telescope frame enabling the non standard cables to be locked safely into position.
In the event that any of the above precautions failed, a large ‘master stop’ switch was mounted in a prominent position on the front plate of the telescope base. It was an industrial grade, large, red, mechanically latching press to stop switch, wired into the end stop circuitry of the telescope drive, so that if ever the switch was activated the drive system would immediately shut down and remain so until the master stop switch was reset to normal operating condition. As an additional safety aid, the dome camera (mentioned earlier under ‘the video system’ p 33 item g) was fitted with four high intensity infra red LEDS so that the operator in the control room below could see a clear picture of attendees inside the dome on his 12” video monitor even during periods when the area was blacked out.
60
fig 26. Control desk with CCTV monitor
61
CHAPTER 8. - A POINTING MODEL
8.1 OPTIONS
Two common methods exist for generating a pointing model. Firstly, the mechanical and optical parameters of the telescope are modelled and the correction factors calculated and introduced into the system. Secondly, a grid map can be used as a foundation of the model where a library of corrections is accumulated in real time for random pointing positions in the sky. This library of corrections can be added to (with every observation if required) culminating in a very extensive set of correction data enabling high pointing accuracy and repeatability anywhere in the sky. A spacing of around 5 degrees between grid points around the sky yields optimal results.
The ACE system uses the grid map concept in its pointing model. In addition to the above mentioned advantages, the grid map system is independent of the telescope’s style of mechanics and optics, and is thus suitable for any telescope in which the ACE system is deployed. Corrections are stored for each grid point and the model compensates for mechanical flexure, bearing errors, polar misalignment errors and refraction as a function of temperature and atmospheric pressure. Provided sufficient correction points exist for neighbouring stars, up to 5 neighbouring grid points are used in the model.
62
8.2 OBSERVATION DATA
The following is a sample set of observation data using the ACE grid map model. To clarify the layout of the following listing, an explanation of the first line is given below. 20050404 is the UT date 032101 is the UT time to a second 2.9305704 is the HA in hours (+ = W, - = E) -2.43…is the Declination 127.777 is the correction in ARCSECONDS for HA -205.255…is the correction in ARCSECONDS in DEC 237.53 is azimuth in degrees 34.72…is altitude in degrees -62.7 is the correction in ARCSECONDS for AZ -236 is the correction in ARCSECONDS for ALT 10.0 is the temperature in degrees Celsius 1000 is the pressure in mb FB was the observer 1788 is the bright star catalogue number and 28Eta Ori is the common name
20050404-032101 2.9305704 -2.4326253 127.7771427 -205.2557429 237.5384808 34.7206851 -62.7135958 -236.1635733 E 10.0 1000.0 FB 1788 28Eta Ori
20050404-032720 3.0251155 6.3035181 125.5909418 -230.4756303 246.7690042 39.6590271 -123.7449545 -244.1994319 E 10.0 1000.0 FB 1790 24Gam Ori
20050404-032929 2.5597752 7.3797017 87.3960669 -142.9729409 241.6100928 45.5598374 -65.2321762 -160.8361352 E 10.0 1000.0 FB 2061 58Alp Ori
63
20050404-033952 1.8981179 12.8199297 95.3869227 -283.7775123 237.0835690 56.3762604 -246.4487400 -265.6883847 E 10.0 1000.0 FB 2484 31Xi Gem
20050404-034603 1.9580830 2.3799053 47.2073136 -138.9923045 226.9718484 47.9053740 -69.1655202 -139.2670983 E 10.0 1000.0 FB 2506 18 Mon
20050404-035033 2.4352842 4.5725447 84.1371636 -107.2552027 236.9175996 44.9164251 -19.7832319 -135.4301528 E 10.0 1000.0 FB 2298 8Eps Mon 20050404-035238 1.2101709 5.1894419 -34.7412788 -116.2396296 214.0140026 56.3130696 -152.5155527 -86.9318369 E 10.0 1000.0 FB 2943 10Alp CMi
20050404-035402 0.0807889 5.7942575 -25.5492894 -120.2127261 182.5184720 61.3904426 -62.2627838 -119.2025719 E 10.0 1000.0 FB 3492 13Rho Hya
20050404-035724 -0.9524950 5.9198336 -126.7231896 -82.4253346 151.8729254 58.6211595 -161.0173677 -125.1356466 E 10.0 1000.0 FB 3915
20050404-040227 -2.0577760 7.2872586 -230.6574206 -107.1600411 126.4679405 50.7424051 -155.5729343 -232.6973369 E 10.0 1000.0 FB 4310 63Chi Leo
20050404-040555 -1.9765225 -0.0400892 -230.9422846 -82.5468702 134.8073834 45.7951699 -199.3907641 -202.0918934 E 10.0 1000.0 FB 4306 62 Leo
64 20050404-041023 -1.3453735 -0.6840786 -153.2776995 -114.1346283 147.4222168 50.1594645 -135.2763945 -170.3353822 E 10.0 1000.0 FB 4119 30Bet Sex
20050404-041207 -0.9431285 -0.4179158 -105.1128564 -114.2736212 156.1789402 52.7614582 -100.9100500 -142.7627071 E 10.0 1000.0 FB 3981 15Alp Sex
20050404-041402 -0.4424744 -1.1862000 -58.5309236 -111.3096296 168.6920921 53.8908302 -67.4711035 -119.3083134 E 10.0 1000.0 FB 3845 35Iot Hya 20050404-041620 -1.9782710 15.3420692 -149.3139911 -234.7262422 118.0892983 57.2370805 153.3712256 -262.5808310 E 10.0 1000.0 FB 4359 70The Leo
20050404-041800 -1.4861274 14.1042475 -103.1636278 -249.8563218 129.7191994 61.4265047 184.2465910 -254.3381097 E 10.0 1000.0 FB 4209 52 Leo
20050404-041903 -0.9721450 13.6370897 -44.7001145 -258.4121554 143.9811680 65.4132661 220.3098995 -245.5255568 E 10.0 1000.0 FB 4035 37 Leo
20050404-042038 -0.3956787 13.9684203 8.1131201 -129.4547968 163.8205213 68.8926294 106.5898092 -123.8927898 E 10.0 1000.0 FB 3866 16Psi Leo
20050404-042232 0.0110661 15.3093022 38.7491853 -165.8733713 180.4899511 70.9268835 110.8888945 -166.1340744 E 10.0 1000.0 FB 3711
65 20050404-042434 0.5493818 15.2701283 60.2408348 -244.2088131 203.2532945 69.4982381 -79.6331665 -249.4769171 E 10.0 1000.0 FB 3510 54 Cnc
20050404-042908 0.5522187 5.9044569 17.9637630 -109.5179452 196.9241667 60.5099939 -18.5302409 -110.5907513 E 10.0 1000.0 FB 3547 16Zet Hya
20050404-043151 -1.0274757 9.2569364 -75.6482290 -109.9221530 147.0417177 61.1745559 -34.2189418 -131.8525130 E 10.0 1000.0 FB 4133 47Rho Leo 20050404-043951 2.5251706 7.3985564 116.0746014 -273.1190917 241.1259570 45.9487147 -173.1575794 -270.8614895 E 10.0 1000.0 FB 2682
20050404-044205 3.0174732 6.2885075 120.0580475 -330.0526884 246.6583421 39.7362194 -227.0630262 -304.5026681 E 10.0 1000.0 FB 2454
20050404-044316 3.4299161 6.9930883 134.3856879 -262.0910312 252.2258159 35.3985664 -154.7974274 -265.6566311 E 10.0 1000.0 FB 2248
20050404-044449 4.1047305 7.4869722 148.7518005 -273.2927509 259.6644983 27.5891991 -157.1306166 -277.5894300 E 10.0 1000.0 FB 1920
20050404-044637 4.5225047 5.0883953 151.2528145 -352.8030935 261.4316536 21.1116382 -217.4096147 -325.6597958 E 10.0 1000.0 FB 1709
20050404-045301 4.5160852 -0.4728325 151.1106048 -331.5002239 256.5862792 17.9352114 -185.1178979 -318.9389861 E 1.0 1000.0 FB 1764
66 20050404-045456 3.9948517 0.9420039 120.5808994 -178.2128939 252.7051348 25.0138473 -73.1222607 -204.7109963 E 1.0 1000.0 FB 2057
20050404-045705 3.4907004 -0.3587889 207.9481606 -354.8908481 246.1532034 30.0299620 -152.0538028 -389.7150644 E 1.0 1000.0 FB 2335
20050404-045849 3.0671180 -1.1907764 189.3947187 -268.2255319 240.3581528 34.1503920 -73.2143767 -322.6972708 E 1.0 1000.0 FB 2572
20050404-050050 4.5542236 15.1853736 273.5719283 -344.4506450 270.9448651 26.2470497 -176.0060452 -404.2593745 E 1.0 1000.0 FB 1809
20050404-050506 5.0955229 14.4875658 289.5623762 -321.5708648 274.7498726 19.1909418 -132.8074309 -407.7423550 E 1.0 1000.0 FB 1600
20050404-050728 3.9933110 14.7108936 291.7423501 -258.2987666 265.6026381 32.9380439 -85.3374770 -375.7573088 E 1.0 1000.0 FB 2159 67Nu Ori
20050404-050946 3.5977301 14.0685517 273.1798592 -345.2515262 261.1867928 37.4594304 -185.3571213 -409.5990186 E 1.0 1000.0 FB 2391
20050404-051108 3.0414396 15.8463872 272.0407194 -312.3067873 257.3287903 45.1915903 -168.1813915 -389.8371905 E 1.0 1000.0 FB 2684 45 Gem
20050404-051317 2.5156941 14.1124850 250.8447381 -336.2283220 248.6602523 50.4141246 -186.0343475 -397.7269198 E 1.0 1000.0 FB 2967
20050404-051519 2.0656630 14.5406519 133.3542989 -295.4828312 242.3191459 55.7553267 -246.6253683 -291.1108436 E 1.0 1000.0 FB 3198
67
20050404-052216 1.5168314 15.2587789 244.7078663 -288.0690765 232.6062920 61.9893631 -48.4943685 -371.7255961 E 1.0 1000.0 FB 3510 54 Cnc
20050404-052353 1.0392266 15.2994172 206.4739090 -203.3431913 220.1844198 66.3150855 134.1734868 -279.4727040 E 1.0 1000.0 FB 3711
20050404-052754 0.6098482 12.9729642 184.9409629 -272.8379631 203.3990072 67.0390494 200.4152065 -317.5212793 E 1.0 1000.0 FB 3896 23 Leo 20050404-052951 0.1287340 14.8860778 161.2952011 -249.3100766 185.5782830 70.4266337 403.2045540 -261.2767473 E 1.0 1000.0 FB 4070 42 Leo
20050404-053143 -0.9721328 15.3391403 90.4527297 -182.6196706 141.8172412 66.8733180 434.9399699 -108.6765586 E 1.0 1000.0 FB 4426 85 Leo
20050404-053450 -2.0425891 17.0084239 -13.0855731 -205.8046533 114.6089493 57.5868307 287.0995856 -137.3112269 E 1.0 1000.0 FB 4801 25 Com
20050404-053622 -2.6900500 13.5818069 -105.7018142 -262.6908381 109.6333975 48.0711306 222.3728472 -239.8107465 E 1.0 1000.0 FB 5013
20050404-053810 -3.6652519 15.2075233 -236.7545870 -144.2347586 96.9432307 37.2406999 2.2295136 -270.1598685 E 1.0 1000.0 FB 5352
68 20050404-054013 -3.5113042 24.9973344 -140.1222403 -264.7928951 86.9512877 43.8058952 260.7410137 -225.5249099 E 1.0 1000.0 FB 5304 12 Boo
20050404-054155 -2.9248722 24.5072947 -58.1262093 -296.9348937 92.5485799 50.8577054 391.2142310 -173.3286096 E 1.0 1000.0 FB 5123
20050404-054415 -2.0811066 24.7665014 20.1590048 -171.0704657 101.1541954 61.3364068 335.4748877 -60.9928160 E 1.0 1000.0 FB 4864
20050404-054550 -0.9768527 25.1371889 167.8706249 -196.6532697 122.1663327 74.3043003 918.2731748 -7.3287068 E 1.0 1000.0 FB 4512 20050404-054800 0.0802264 26.2252711 241.1372443 -272.9022050 187.5698691 81.7777585 1281.8756949 -296.5871423 E 1.0 1000.0 FB 4189 40 LMi
20050404-055032 1.0756898 23.6851922 270.4077590 -250.6288562 237.0055796 72.3359572 -90.9339034 -351.2059535 E 1.0 1000.0 FB 3873 17Eps Leo
20050404-055351 1.8498427 24.3747625 306.5864284 -227.4100917 254.8754091 63.9410342 -145.4886267 -354.3889043 E 1.0 1000.0 FB 3595 69Nu Cnc
20050404-055744 3.0688543 26.6620417 340.0695434 -353.2290668 271.7785947 49.9454202 -326.0847591 -416.0825787 E 1.0 1000.0 FB 3067 83Phi Gem
20050404-055920 4.0652225 25.2818028 347.2695879 -356.6670786 277.5457472 37.0995995 -237.6181762 -435.7413740 E 1.0 1000.0 FB 2569 37 Gem
69
20050404-060059 5.0652836 24.1662622 364.8760221 -373.9973571 283.5322642 24.4315389 -187.6783888 -470.5720742 E 1.0 1000.0 FB 2074
20050404-060300 5.5594937 25.1084492 385.0009588 -260.8141062 287.9479342 19.0028327 -55.7599304 -432.1004982 E 1.0 1000.0 FB 1821118 Tau
20050404-060443 5.5160606 34.6536981 411.8026800 -343.6185185 296.7093561 24.0091061 -173.1661493 -455.7365491 E 1.0 1000.0 FB 1854
20050404-060636 4.8473479 36.1174103 387.7663179 -154.1776446 294.4617872 32.0731410 -33.5673254 -347.8928531 E 1.0 1000.0 FB 2217
20050404-060858 4.0447288 34.3783825 366.3729396 -348.9528725 288.2821371 40.7304597 -312.8595398 -396.2068193 E 1.0 1000.0 FB 2660
20050404-062019 3.3059754 35.3566314 373.0214753 -174.6565418 286.0803937 49.7386414 -153.4132873 -336.4373194 E 1.0 1000.0 FB 3130
20050404-062233 2.0683408 35.2376453 352.3100656 -388.8446953 280.8806895 64.6162434 -820.0191439 -332.7811173 E 1.0 1000.0 FB 3686
20050404-062547 0.9657010 36.5732186 352.2235356 -389.9062983 284.6876586 78.0142305 -2026.0999863 -236.3250924 E 1.0 1000.0 FB 4100 31Bet LMi
20050404-062725 0.1486531 32.9633631 276.7540692 -370.7971624 233.2283798 87.6643928 -3854.1760509 -409.7280804 E 1.0 1000.0 FB 4377 54Nu UMa
70 20050404-063005 -1.0622515 33.2648556 218.1758237 -325.4156514 90.3376094 76.7295793 1522.9975958 128.8293050 E 1.0 1000.0 FB 4784
20050404-063313 -2.0721192 36.1955750 124.8520547 -255.2196609 76.8835806 64.6728436 614.8393819 77.7509485 E 1.0 1000.0 FB 5127 25 CVn
20050404-063503 -2.8889225 36.0811653 55.8521545 -326.5767564 74.4739188 54.8569747 572.2738151 -13.6209650 E 1.0 1000.0 FB 5416
20050404-063644 -3.3240358 32.1954450 -38.1884418 -301.5397777 78.4963549 48.6856378 422.3749008 -119.4355490 E 1.0 1000.0 FB 5569
20050404-063847 -3.1810686 48.6010669 138.8680102 -333.7347351 53.0635240 52.2595793 533.0044945 115.2593091 E 1.0 1000.0 FB 5538 39 Boo
20050404-064034 -2.9708731 44.2921222 140.9827319 -307.9001211 60.1420231 54.6100276 529.3603911 104.4857912 E 1.0 1000.0 FB 5468 33 Boo
20050404-064241 -1.8744205 44.0698928 248.7118952 -345.4751375 57.4455477 66.3144994 719.5851661 259.6796434 E 1.0 1000.0 FB 5116
20050404-064513 -0.9948887 45.3165011 401.9846527 -327.7147415 41.7235006 74.2109656 291.5701864 425.2432128 E 1.0 1000.0 FB 4846
20050404-064758 0.0364510 47.6367303 481.9376924 -396.6100685 358.3937091 76.7387767 -1459.6598219 386.6924639 E 1.0 1000.0 FB 4518 63Chi UMa
71 20050404-065700 0.3085924 44.9670481 422.2186730 -395.9953985 342.8480526 78.8363752 -2135.7242425 271.5801718 E 1.0 1000.0 FB 4486
20050404-065830 0.9746028 45.3871606 452.7378615 -393.4540598 318.9761697 74.3324083 -1872.1390056 8.0123413 E 1.0 1000.0 FB 4280
20050404-070007 2.0392999 45.2776933 468.8864072 -404.7530531 304.3058587 64.3102519 -1095.8007708 -217.5204322 E 1.0 1000.0 FB 3929
20050404-070208 3.0911822 45.5070619 477.6389466 -389.3805496 301.8916327 53.3143153 -663.3386548 -326.7059079 E 1.0 1000.0 FB 3545
20050404-070406 3.6110462 45.5341542 494.4470120 -382.5556651 302.1842816 47.8558842 -531.0330712 -373.3237191 E 1.0 1000.0 FB 3309
20050404-070613 4.1349331 43.8681656 486.5098467 -370.0155842 300.8932630 42.1017519 -402.7074946 -413.0438659 E 1.0 1000.0 FB 3094
20050404-070747 5.1715063 45.0195850 499.0229373 -290.6468314 305.8002665 31.6673155 -190.9398101 -427.0255341 E 1.0 1000.0 FB 2585 16 Lyn
20050404-071056 5.4663791 44.4321597 513.7143228 -369.7999401 306.4142200 28.5152156 -238.9724616 -476.4917879 E 1.0 1000.0 FB 2459 55Psi4Aur
20050404-071625 6.2765672 45.9101503 523.4777161 -184.7545716 311.8328385 21.3496672 7.1897928 -408.2020558 E 1.0 1000.0 FB 2091 35Pi Aur
72 20050404-071806 6.5289486 56.0944461 624.4969995 -161.7885531 322.8215166 23.8995367 11.8590025 -383.7594668 E 1.0 1000.0 FB 1969 26 Cam
20050404-072004 7.2307986 54.3499267 648.2525075 -348.0332872 324.4931391 17.8515320 -75.9017217 -508.2577781 E 1.0 1000.0 FB 1630
20050404-072132 5.7861600 55.3106022 606.8441385 -191.8432237 319.2990695 29.3806829 -79.9864013 -388.6801759 E 1.0 1000.0 FB 2376 7 Lyn 20050404-072628 5.1508780 52.0194464 520.7061301 -407.0635056 313.7140411 33.8545022 -381.4253526 -409.7823084 E 1.0 1000.0 FB 2737
20050404-072835 4.1757372 54.0112739 548.9717189 -436.9896761 314.6338631 42.8304061 -581.9822216 -335.9030512 E 1.0 1000.0 FB 3246
20050404-073011 3.0113348 55.5985486 545.9210851 -448.3528640 318.6949309 52.6239147 -847.9590073 -176.5891893 E 1.0 1000.0 FB 3747
20050404-073139 2.0231103 55.8281003 560.8878082 -442.7677073 325.2516413 60.1403423 -1090.2493547 -19.6093599 E 1.0 1000.0 FB 4112 36 UMa
20050404-073531 1.0959024 54.1998211 579.4369320 -462.0787035 334.8472431 67.0787283 -1403.6283173 169.1844785 E 1.0 1000.0 FB 4427
20050404-073948 0.2127267 55.5535169 596.8587470 -444.2698527 355.0245426 68.7137955 -1069.2891649 399.4519467 E 1.0 1000.0 FB 4745 73 UMa
73 20050404-074150 -0.9732088 54.5311517 485.1816786 -416.3668090 22.3873163 67.4191261 -26.6324258 502.2862665 E 1.0 1000.0 FB 5154 83 UMa
20050404-074356 -1.8974699 53.8770942 392.5491085 -412.9935857 36.9165935 62.1120667 473.9217921 417.9023340 E 1.0 1000.0 FB 5467
20050404-074641 -3.0081801 55.2553194 302.3869244 -346.4696235 41.8398478 52.7397571 478.6877186 256.0067420 E 1.0 1000.0 FB 5887 20050404-074849 -1.4476099 51.2211411 411.1681763 -410.2970536 36.3577861 66.9909041 407.9375124 457.0979574 E 1.0 1000.0 FB 5350 21Iot Boo
20050404-075156 -0.7007006 48.8624703 446.2459413 -432.9590994 25.0912946 73.5612008 -61.4220195 522.6142784 E 1.0 1000.0 FB 5112 24 CVn
20050404-075351 -0.7218057 36.1602453 284.7071587 -378.4114760 75.5254546 80.9885035 2163.8033646 283.0208093 E 1.0 1000.0 FB 5127 25 CVn
20050404-075653 -2.3788041 51.8204650 342.1761162 -398.4838583 44.6314302 59.1227414 584.4762203 336.4488320 E 1.0 1000.0 FB 5715
20050404-082051 -2.8381773 67.0135269 825.7180893 -372.0612756 23.8580943 49.2184592 231.9606324 467.9188036 E -2.0 1000.0 FB 6069
20050404-082244 -2.1197586 64.0710919 673.9204710 -383.2515196 23.4019516 54.5446792 160.4084306 474.0227359 E -2.0 1000.0 FB 5785
74 20050404-082447 -0.6439637 64.2219297 748.7172559 -418.4956198 8.2858048 59.5790978 -388.0401414 491.8845308 E -2.0 1000.0 FB 5291 11Alp Dra
20050404-082740 0.0256661 64.5711997 781.9035952 -451.6993453 359.6712673 59.8097218 -671.9326989 449.0361028 E -2.0 1000.0 FB 5074
20050404-082924 1.0850441 63.6407283 756.6506058 -446.1713361 345.9925898 59.0632460 -970.0584464 249.4742741 E -2.0 1000.0 FB 4727 20050404-083037 1.1068707 63.6387147 835.4139836 -453.4789163 345.7390843 58.9990587 -1039.1896372 235.8224890 E -2.0 1000.0 FB 4727
20050404-083312 2.1854096 64.1794608 809.8133383 -418.6911345 336.2563352 54.1487512 -933.8834458 4.1058178 E -2.0 1000.0 FB 4391
20050404-083938 0.0859124 -0.6571694 122.0691645 -158.8434551 182.2436470 54.9401730 203.6753018 -162.6568861 E -2.0 1000.0 FB 5107 79Zet Vir
20050404-084214 0.2872060 -11.2165461 115.3976302 -155.3251525 185.9011843 44.2184769 138.7324160 -164.5065428 E -2.0 1000.0 FB 5056 67Alp Vir
20050404-084436 -0.9723651 -5.7137131 40.0806582 -160.6901821 158.1835522 47.6043839 129.8320754 -140.5513566 E -2.0 1000.0 FB 5487107Mu Vir
20050404-084716 -1.7811959 -10.1079617 -45.1316181 -148.9840015 145.3920703 38.8017052 40.9024960 -152.1680911 E -2.0 1000.0 FB 5777 37 Lib
75 20050404-092004 0.0445458 35.3784150 350.8457346 -370.9677565 331.3784885 88.8626252 -20642.8311679 207.5646677 E -2.0 1000.0 FB 5361
20050404-092252 0.6788373 34.8594525 358.8457115 -361.0259302 276.1513964 81.6104677 -2511.8920284 -289.6579812 E -2.0 1000.0 FB 5161
20050404-092437 1.2213838 27.7420694 269.3554763 -394.9315545 252.0188474 72.9929224 -826.8650196 -393.2157363 E -2.0 1000.0 FB 4983 43Bet Com 20050404-092754 -0.5565473 40.2489742 345.8150093 -412.9132790 46.0597855 81.1472715 1000.8908836 464.7312228 E -2.0 1000.0 FB 5602 42Bet Boo
20050404-092900 0.7812572 34.8561575 356.0808619 -372.8258599 276.1426562 80.3498318 -2227.3783408 -293.2998986 E -2.0 1000.0 FB 5161
20050404-093111 0.4663308 64.2069192 821.9365785 -472.2422419 353.9405333 59.8684261 -880.4393452 392.8579448 E -2.0 1000.0 FB 5291 11Alp Dra
20050404-093327 1.1252246 64.5593011 840.0217547 -496.1917157 346.3383551 58.1248402 -1030.5424566 281.0022721 E -2.0 1000.0 FB 5074
20050404-093838 2.1061247 69.6081564 1015.2870740 -507.9735402 343.2362039 50.7382968 -953.9769130 132.5618773 E -2.0 1000.0 FB 4787 5Kap Dra
20050404-094318 3.0315473 66.5714478 928.6874382 -500.3085663 334.7049772 48.4394743 -926.0287931 -93.1300693 E -2.0 1000.0 FB 4504 3 Dra
76 20050404-094538 3.7126468 61.5861128 740.2701018 -487.1536772 325.6180289 45.8924832 -788.9525420 -244.3263798 E -2.0 1000.0 FB 4301 50Alp UMa
20050404-094759 5.2867042 62.9266286 791.1152859 -432.9672160 326.9424490 34.9291618 -459.4187283 -418.2114566 E -2.0 1000.0 FB 3757 23 UMa 20050404-095053 6.2084952 64.9618403 929.7736555 -200.4592240 330.9489401 29.5104369 -74.0084458 -436.5327085 E -2.0 1000.0 FB 3391 3Pi 1UMa
20050404-095351 7.1324383 65.4183808 933.2173518 -176.9222946 334.0946113 24.4077680 43.1017190 -424.4822784 E -2.0 1000.0 FB 2975 51 Cam
20050404-095549 7.4863224 66.2772775 974.7100684 -259.1901448 336.1441106 23.0185152 2.7767931 -469.5785176 E -2.0 1000.0 FB 2809
20050404-100930 7.1725210 73.8327125 1358.2167894 -329.2459670 342.4675400 28.2250356 -142.8249567 -484.5852409 E -2.0 1000.0 FB 3075
20050404-101208 5.7574492 74.9696706 1409.9820202 -410.2225564 341.8128910 33.9844112 -442.8309355 -407.8518400 E -2.0 1000.0 FB 3719
20050404-101415 4.6750340 75.5561806 1459.8083030 -467.3902378 342.6608299 38.0856355 -664.0361346 -277.4696770 E -2.0 1000.0 FB 4126
20050404-101607 2.9821716 74.9711350 1446.3769532 -542.4769865 345.2471378 44.2201683 -918.3775846 18.5351499 E -2.0 1000.0 FB 4687
77 20050404-101923 1.2412906 74.4031136 1483.6887765 -536.9332527 352.4882672 48.9548035 -878.5602223 335.4096482 E -2.0 1000.0 FB 5305 3 UMi
20050404-102308 -0.2982477 77.6115283 2065.8752751 -521.8391473 1.3988453 46.7251968 -562.8567982 563.1920768 E -2.0 1000.0 FB 5903 16Zet UMi
20050404-102516 -1.5637494 75.1256339 1554.4785158 -515.9168027 8.7397923 47.7424055 -136.5849628 644.5413986 E -2.0 1000.0 FB 6379
20050404-102826 4.4277639 61.5921536 -458846.6273993 -99802.2866462 324.8150902 40.8280082 1168623.4652658 25600.8211440 E -2.0 1000.0 FB 424 1Alp UMi
20050404-103051 2.9245054 59.3045083 668.0641120 -533.8624864 324.8191694 52.1213686 -1012.5780056 -120.6929127 E -2.0 1000.0 FB 4800
20050404-103325 2.1021629 59.7672728 731.9033297 -514.6290603 330.7750866 57.3611068 -1172.2579397 16.8020153 E -2.0 1000.0 FB 5085
20050404-103459 0.1405461 60.4972983 712.0577891 -508.2801761 357.6442745 63.8487503 -865.6553997 484.2686879 E -2.0 1000.0 FB 5755
20050404-103657 -1.7906358 59.8961439 589.0160637 -479.4183262 26.1626758 59.0727359 282.0089627 543.7577448 E -2.0 1000.0 FB 6511
20050404-103908 2.1974295 59.7700186 725.7132718 -505.2342067 330.0030564 56.7767081 -1137.1261474 -6.9009435 E -2.0 1000.0 FB 5085
78 20050405-031146 1.4990522 -16.7550750 137.5706165 -191.9971015 206.4062509 34.5678665 58.4735265 -227.8242667 E -2.0 1000.0 FB 2491 9Alp CMa
20050405-031845 2.1208836 -6.3253017 218.8270520 -236.1702115 222.6958717 39.4069928 60.6361232 -317.6384221 E -2.0 1000.0 FB 2227 5Gam Mon
20050405-032229 2.6351228 -9.7138431 239.9483361 -238.9572494 227.8119060 32.1516520 44.0965704 -334.1486526 E -2.0 1000.0 FB 2004 53Kap Ori
20050405-032407 2.8679641 -5.9542481 256.7025276 -240.1886494 233.8210668 32.7895578 34.2403154 -349.3678801 E -2.0 1000.0 FB 1899 44Iot Ori
20050405-032541 3.2421097 -8.2464697 264.0664210 -265.0013498 236.7079248 27.3095399 3.0563349 -372.1928923 E -2.0 1000.0 FB 1713 19Bet Ori
20050405-032651 3.1774003 -13.2047125 248.7607705 -216.5203391 232.1700581 24.3402706 38.4224927 -322.9918286 E -2.0 1000.0 FB 1756 6Lam Lep
20050405-032952 3.9171686 -14.3647356 274.0814967 -394.4397331 239.4688339 15.9360764 -113.3735427 -462.8575869 E -2.0 1000.0 FB 1481 53 Eri
20050405-033144 3.8504294 -8.5587625 273.5671864 -338.1930177 243.2945614 20.5708103 -76.7430184 -427.1013611 E -2.0 1000.0 FB 1508 56 Eri
79
20050405-034025 4.5320424 -6.9011944 316.4651143 -424.3233889 251.4211596 13.8466012 -145.1665342 -508.8465168 E -2.0 1000.0 FB 1298 38Omi1Eri
20050405-034326 4.8748604 -3.0156572 331.4589132 -435.3458064 257.7698338 12.0964724 -160.0631634 -524.0393187 E -2.0 1000.0 FB 1212 32 Eri
20050405-034844 4.2318382 -14.3414875 281.8970058 -342.6928450 242.6318217 12.5428811 -82.5255253 -430.7830167 E -2.0 1000.0 FB 1481 53 Eri
20050405-035645 3.4573675 -17.8568864 243.0639551 -267.8952566 231.9937747 18.1778318 -14.7260095 -353.7223136 E -2.0 1000.0 FB 1865 11Alp Lep
20050405-035838 3.0943737 -14.1948600 221.6023080 -198.3359887 230.4549688 24.4013260 35.0817196 -290.6595041 E -2.0 1000.0 FB 2085 16Eta Lep
20050405-040108 2.1728883 -12.0794700 176.8554937 -196.2801519 219.5461448 34.1769804 48.8912066 -258.4674834 E -2.0 1000.0 FB 2574 14The CMa
20050405-040437 0.9832478 -19.2878317 125.7551415 -179.9069804 196.9573720 34.5255730 83.7233693 -204.2181828 E -2.0 1000.0 FB 3192 16 Pup
80 20050405-041909 0.0462210 -12.0291297 72.3911150 -175.8272748 180.9361431 43.5843628 94.4827118 -176.7734528 E -2.0 1000.0 FB 3706 26 Hya
20050405-042211 -0.7511646 -12.4089700 -5.1775033 -166.0268805 165.1209437 41.9998625 41.8638220 -163.1664691 E -2.0 1000.0 FB 3994 41Lam Hya
20050405-042531 -1.5235322 -14.1348178 -75.7474236 -153.6051942 151.9282020 36.8399583 -7.2550529 -170.1686687 E -2.0 1000.0 FB 4289
20050405-042832 -1.6648364 -22.8594286 -133.2053091 -117.1279125 153.8488254 28.0346923 -75.4535907 -156.0599998 E -2.0 1000.0 FB 4343 11Bet Crt
20050405-045812 -1.5283622 -16.3258097 -95.1198360 -133.6248515 152.9190021 34.8003350 -38.6278271 -158.6961769 E -2.0 1000.0 FB 4451
20050405-050214 -1.5570852 -24.7507586 -101.0864640 -106.8362623 156.2010259 26.8488769 -51.8551529 -133.0546705 E -2.0 1000.0 FB 4489
20050405-054525 -0.8343624 -24.7549689 -19.5789021 -114.7114313 166.9083402 29.6817010 7.1504295 -115.9151982 E -2.0 1000.0 FB 4489
20050405-054815 0.2981377 -23.7769031 89.4922658 -109.2044195 184.8101571 31.6863123 86.3147078 -115.0712066 E -2.0 1000.0 FB 4145 44 Hya
20050405-055018 1.2908131 -24.7344667 154.6611275 -132.3593233 199.9583341 28.0928782 104.9431264 -169.3813323 E -2.0 1000.0 FB 3828
81 20050405-055258 2.3940155 -24.6336031 221.9870673 -153.5023673 215.0586837 21.8528920 99.3808024 -236.1982071 E 5.0 1000.0 FB 3381
20050405-055442 3.1524801 -24.8779822 257.0961670 -174.5965172 223.8167451 15.6823351 74.0896892 -282.5234802 E 5.0 1000.0 FB 3045 7Xi Pup
20050405-055624 3.4491993 -24.7223850 269.2383063 -180.5674885 227.0984103 13.1825972 64.1838278 -297.5481753 E 5.0 1000.0 FB 2900
20050405-055823 3.7983024 -10.0109422 272.1880341 -302.1566853 241.5937426 20.1683400 -44.2843882 -401.7934194 E 5.0 1000.0 FB 2732
20050405-060000 2.7561900 -12.6782447 244.3433124 -184.3702420 227.2966187 28.7219041 82.3615425 -292.6067788 E 5.0 1000.0 FB 3259
20050405-060153 0.5764297 -13.6484392 108.3795209 -181.8200818 191.2082150 41.2711386 98.3837890 -196.6971047 E 5.0 1000.0 FB 4123
20050405-060350 2.8203247 -12.6815397 227.6301977 -202.7902519 228.1267197 28.1319924 50.8411276 -297.3961281 E 5.0 1000.0 FB 3259
20050405-060711 -0.4640442 -13.2634733 49.7046009 -177.8183323 170.8819602 41.8973213 96.5894500 -169.6913909 E 5.0 1000.0 FB 4488 24Iot Crt
20050405-061536 -0.3561340 21.2271222 188.5246858 -359.6671423 158.9332303 76.0289420 1170.2009156 -284.3321321 E 5.0 1000.0 FB 4495 92 Leo
82 20050405-061924 -1.5023048 21.1236958 101.7802350 -344.0571140 117.8798597 66.1445193 812.7745626 -139.6342246 E 5.0 1000.0 FB 4894 35 Com
20050405-061944 -1.4966066 21.1236958 101.9360683 -344.0379291 118.0029805 66.2068358 814.4757941 -139.9760709 E 5.0 1000.0 FB 4894 35 Com
20050405-062332 -0.1835512 33.5409033 336.0113588 -201.3047480 109.4431988 87.5665957 6644.2557339 193.8378337 E 5.0 1000.0 FB 4482
20050405-070158 -1.3949816 47.0493050 370.4762652 -406.6751797 44.8446552 69.8134214 623.8936029 427.0356068 E 5.0 1000.0 FB
To observe any trends associated with the above data, a scatter plot of correction vectors against their prime value (i.e. DEC –v- DEC correction) is shown below.
HA HA Corr Azimuth Alt Az Corr Alt Corr -3.6653 -236.755 246.769 39.65903 -123.745 -244.199 -1.9765 -230.942 241.6101 45.55984 -65.2322 -160.836 -2.0578 -230.657 237.0836 56.37626 -246.449 -265.688 -1.3454 -153.278 226.9718 47.90537 -69.1655 -139.267 -1.9783 -149.314 236.9176 44.91643 -19.7832 -135.43 -3.5113 -140.122 214.014 56.31307 -15.5156 -86.9318 -1.6648 -133.205 182.5185 61.39044 -62.2628 -119.203
83 -0.9525 -126.723 151.8729 58.62116 -161.017 -125.136 -2.6901 -105.702 126.4679 50.74241 -155.573 -232.697 -0.9431 -105.113 134.8074 45.79517 -199.391 -202.092 -1.4861 -103.164 147.4222 50.15946 -135.276 -170.335 -1.5571 -101.086 156.1789 52.76146 -100.91 -142.763 -1.5284 -95.1198 168.6921 53.89083 -67.4711 -119.308 -1.5235 -75.7474 118.0893 57.23708 153.3712 -262.581 -1.0275 -75.6482 129.7192 61.4265 184.2466 -254.338 -0.4425 -58.5309 143.9812 65.41327 220.3099 -245.526 -2.9249 -58.1262 163.8205 68.89263 106.5898 -123.893 -1.7812 -45.1316 180.49 70.92688 110.8889 -166.134 -0.9721 -44.7001 203.2533 69.49824 -79.6332 -249.477 -3.324 -38.1884 196.9242 60.50999 -18.5302 -110.591 1.21017 -34.7413 147.0417 61.17456 -34.2189 -131.853 0.08079 -25.5493 241.126 45.94871 -173.158 -270.861 -0.8344 -19.5789 246.6583 39.73622 -227.063 -304.503 -2.0426 -13.0856 252.2258 35.39857 -154.797 -265.657 -0.7512 -5.1775 259.6645 27.5892 -157.131 -277.589 -0.3957 8.11312 261.4317 21.11164 -217.41 -325.66 0.55222 17.96376 256.5863 17.93521 -185.118 -318.939 -2.0811 20.159 252.7051 25.01385 -73.1223 -204.711 0.01107 38.74919 246.1532 30.02996 -152.054 -389.715 -0.9724 40.08066 240.3582 34.15039 -73.2144 -322.697 1.95808 47.20731 270.9449 26.24705 -176.006 -404.259 -0.464 49.7046 274.7499 19.19094 -132.807 -407.742 -2.8889 55.85215 265.6026 32.93804 -85.3375 -375.757 0.54938 60.24083 261.1868 37.45943 -185.357 -409.599 0.04622 72.39112 257.3288 45.19159 -168.181 -389.837 2.43528 84.13716 248.6603 50.41412 -186.034 -397.727 2.55978 87.39607 242.3191 55.75533 -246.625 -291.111 0.29814 89.49227 232.6063 61.98936 -48.4944 -371.726 -0.9721 90.45273 220.1844 66.31509 134.1735 -279.473 1.89812 95.38692 203.399 67.03905 200.4152 -317.521 -1.5023 101.7802 185.5783 70.42663 403.2046 -261.277 -1.4966 101.9361 141.8172 66.87332 434.94 -108.677 0.57643 108.3795 114.6089 57.58683 287.0996 -137.311 0.28721 115.3976 109.6334 48.07113 222.3728 -239.811 2.52517 116.0746 96.94323 37.2407 2.229514 -270.16 3.01747 120.058 86.95129 43.8059 260.741 -225.525 3.99485 120.5809 92.54858 50.85771 391.2142 -173.329 0.08591 122.0692 101.1542 61.33641 335.4749 -60.9928
84 -2.0721 124.8521 122.1663 74.3043 918.2732 -7.32871 3.02512 125.5909 187.5699 81.77776 1281.876 -296.587 0.98325 125.7551 237.0056 72.33596 -90.9339 -351.206 2.93057 127.7771 271.7786 49.94542 -326.085 -416.083 2.06566 133.3543 277.5457 37.0996 -237.618 -435.741 3.42992 134.3857 283.5323 24.43154 -187.678 -470.572 1.49905 137.5706 287.9479 19.00283 -55.7599 -432.1 -3.1811 138.868 296.7094 24.00911 -173.166 -455.737 -2.9709 140.9827 294.4618 32.07314 -33.5673 -347.893 4.10473 148.7518 288.2821 40.73046 -312.86 -396.207 4.51609 151.1106 286.0804 49.73864 -153.413 -336.437 4.5225 151.2528 280.8807 64.61624 -820.019 -332.781 1.29081 154.6611 284.6877 78.01423 -2026.1 -236.325 0.12873 161.2952 233.2284 87.66439 -3854.18 -409.728 -0.9769 167.8706 90.33761 76.72958 1522.998 128.8293 2.17289 176.8555 76.88358 64.67284 614.8394 77.75095 0.60985 184.941 74.47392 54.85697 572.2738 -13.621 -0.3561 188.5247 78.49635 48.68564 422.3749 -119.436 3.06712 189.3947 53.06352 52.25958 533.0045 115.2593 1.03923 206.4739 60.14202 54.61003 529.3604 104.4858 3.4907 207.9482 57.44555 66.3145 719.5852 259.6796 -1.0623 218.1758 41.7235 74.21097 291.5702 425.2432 2.12088 218.8271 358.3937 76.73878 -1459.66 386.6925 3.09437 221.6023 342.8481 78.83638 -2135.72 271.5802 2.39402 221.9871 318.9762 74.33241 -1872.14 8.012341 2.82032 227.6302 304.3059 64.31025 -1095.8 -217.52 2.63512 239.9483 301.8916 53.31432 -663.339 -326.706 0.08023 241.1372 302.1843 47.85588 -531.033 -373 3.45737 243.064 300.8933 42.10175 -402.707 -413.044 2.75619 244.3433 305.8003 31.66732 -190.94 -427.026 1.51683 244.7079 306.4142 28.51522 -238.972 -476.492 -1.8744 248.7119 311.8328 21.34967 7.189793 -408.202 3.1774 248.7608 322.8215 23.89954 11.859 -383.759 2.51569 250.8447 324.4931 17.85153 -75.9017 -508.258 2.86796 256.7025 319.2991 29.38068 -79.9864 -388.68 3.15248 257.0962 313.714 33.8545 -381.425 -409.782 3.24211 264.0664 314.6339 42.83041 -581.982 -335.903 3.4492 269.2383 325.2516 60.14034 -1090.25 -19.6094 1.22138 269.3555 334.8472 67.07873 -1403.63 169.1845 1.07569 270.4078 355.0245 68.7138 -1069.29 399.4519 3.04144 272.0407 22.38732 67.41913 -26.6324 502.2863
85 3.7983 272.188 36.91659 62.11207 473.9218 417.9023 3.59773 273.1799 41.83985 52.73976 478.6877 256.0067 3.85043 273.5672 36.35779 66.9909 407.9375 457.098 4.55422 273.5719 25.09129 73.5612 -61.422 522.6143 3.91717 274.0815 75.52545 80.9885 2163.803 283.0208 0.14865 276.7541 44.63143 59.12274 584.4762 336.4488 4.23184 281.897 23.85809 49.21846 231.9606 467.9188 -0.7218 284.7072 23.40195 54.54468 160.4084 474.0227 5.09552 289.5624 8.285805 59.5791 -388.04 491.8845 3.99331 291.7424 359.6713 59.80972 -671.933 449.0361 -3.0082 302.3869 345.9926 59.06325 -970.058 249.4743 4.53204 316.4651 345.7391 58.99906 -1039.19 235.8225 4.87486 331.4589 336.2563 54.14875 -933.883 4.105818 -0.1836 336.0114 182.2436 54.94017 203.6753 -162.657 3.06885 340.0695 185.9012 44.21848 138.7324 -164.507 -2.3788 342.1761 158.1836 47.60438 129.8321 -140.551 -0.5565 345.815 145.3921 38.80171 40.9025 -152.168 4.06522 347.2696 331.3785 88.86263 -20642.8 207.5647 0.04455 350.8457 276.1514 81.61047 -2511.89 -289.658 0.9657 352.2235 252.0188 72.99292 -826.865 -393.216 2.06834 352.3101 46.05979 81.14727 1000.891 464.7312 0.78126 356.0809 276.1427 80.34983 -2227.38 -293.3 0.67884 358.8457 353.9405 59.86843 -880.439 392.8579 5.06528 364.876 346.3384 58.12484 -1030.54 281.0023 4.04473 366.3729 343.2362 50.7383 -953.977 132.5619 -1.395 370.4763 334.705 48.43947 -926.029 -93.1301 3.30598 373.0215 325.618 45.89248 -788.953 -244.326 5.55949 385.001 326.9424 34.92916 -459.419 -418.211 4.84735 387.7663 330.9489 29.51044 -74.0084 -436.533 -1.8975 392.5491 334.0946 24.40777 43.10172 -424.482 -0.9949 401.9847 336.1441 23.01852 2.776793 -469.579 -1.4476 411.1682 342.4675 28.22504 -142.825 -484.585 5.51606 411.8027 341.8129 33.98441 -442.831 -407.852 0.30859 422.2187 342.6608 38.08564 -664.036 -277.47 -0.7007 446.2459 345.2471 44.22017 -918.378 18.53515 0.9746 452.7379 352.4883 48.9548 -878.56 335.4096 2.0393 468.8864 1.398845 46.7252 -562.857 563.1921 3.09118 477.6389 8.739792 47.74241 -136.585 644.5414 0.03645 481.9377 324.8151 40.82801 1168623 25600.82 -0.9732 485.1817 324.8192 52.12137 -1012.58 -120.693 4.13493 486.5098 330.7751 57.36111 -1172.26 16.80202
86 3.61105 494.447 357.6443 63.84875 -865.655 484.2687 5.17151 499.0229 26.16268 59.07274 282.009 543.7577 5.46638 513.7143 330.0031 56.77671 -1137.13 -6.90094 5.15088 520.7061 206.4063 34.56787 58.47353 -227.824 6.27657 523.4777 222.6959 39.40699 60.63612 -317.638 4.17574 548.9717 227.8119 32.15165 44.09657 -334.149 2.02311 560.8878 233.8211 32.78956 34.24032 -349.368 1.0959 579.4369 236.7079 27.30954 3.056335 -372.193 -1.7906 589.0161 232.1701 24.34027 38.42249 -322.992 0.21273 596.8587 239.4688 15.93608 -113.374 -462.858 5.78616 606.8441 243.2946 20.57081 -76.743 -427.101 6.52895 624.497 251.4212 13.8466 -145.167 -508.847 7.2308 648.2525 257.7698 12.09647 -160.063 -524.039 2.92451 668.0641 242.6318 12.54288 -82.5255 -430.783 -2.1198 673.9205 231.9938 18.17783 -14.726 -353.722 0.14055 712.0578 230.455 24.40133 35.08172 -290.66 2.19743 725.7133 219.5461 34.17698 48.89121 -258.467 2.10216 731.9033 196.9574 34.52557 83.72337 -204.218 3.71265 740.2701 180.9361 43.58436 94.48271 -176.773 -0.644 748.7173 165.1209 41.99986 41.86382 -163.166 1.08504 756.6506 151.9282 36.83996 -7.25505 -170.169 0.02567 781.9036 153.8488 28.03469 -75.4536 -156.06 5.2867 791.1153 152.919 34.80034 -38.6278 -158.696 2.18541 809.8133 156.201 26.84888 -51.8552 -133.055 0.46633 821.9366 166.9083 29.6817 7.15043 -115.915 -2.8382 825.7181 184.8102 31.68631 86.31471 -115.071 1.10687 835.414 199.9583 28.09288 104.9431 -169.381 1.12522 840.0218 215.0587 21.85289 99.3808 -236.198 3.03155 928.6874 223.8167 15.68234 74.08969 -282.523 6.2085 929.7737 227.0984 13.1826 64.18383 -297.548 7.13244 933.2174 241.5937 20.16834 -44.2844 -401.793 7.48632 974.7101 227.2966 28.7219 82.36154 -292.607 2.10612 1015.287 191.2082 41.27114 98.38379 -196.697 7.17252 1358.217 228.1267 28.13199 50.84113 -297.396 5.75745 1409.982 170.882 41.89732 96.58945 -169.691 2.98217 1446.377 158.9332 76.02894 1170.201 -284.332 4.67503 1459.808 117.8799 66.14452 812.7746 -139.634 1.24129 1483.689 118.003 66.20684 814.4758 -139.976 -1.5637 1554.479 109.4432 87.5666 6644.256 193.8378
Table 1...Spread sheet layout of HA prime unit and correction
87
HA vs HA Corr
2500
2000
1500
1000 HA Corr
HA Corr Arcseconds
500
0 -6-4-20246810
-500 HA
fig 27. Scatter plot of HA prime unit v correction
Dec Dec Corr - 74.97114 542.477 - 74.40311 536.933 - 59.30451 533.862 - 77.61153 521.839 - 75.12563 515.917 - 59.76727 514.629 60.4973 -508.28 - 69.60816 507.974 - 59.77002 505.234 - 66.57145 500.309 - 64.5593 496.192 - 61.58611 487.154 59.89614 -
88 479.418 - 64.20692 472.242 75.55618 -467.39 - 54.19982 462.079 - 63.63871 453.479 - 64.5712 451.699 - 63.64073 446.171 55.55352 -444.27 - 55.8281 442.768 54.01127 -436.99 - -3.01566 435.346 - 62.92663 432.967 - 48.86247 432.959 - -6.90119 424.323 - 64.17946 418.691 - 64.22193 418.496 - 54.53115 416.367 - 53.87709 412.994 - 40.24897 412.913 - 51.22114 410.297 - 74.96967 410.223 - 52.01945 407.064 - 47.04931 406.675 - 45.27769 404.753 - 51.82047 398.484 47.63673 -396.61 - 44.96705 395.995 - 27.74207 394.932 -14.3647 -394.44 - 45.38716 393.454 36.57322 -
89 389.906 - 45.50706 389.381 - 35.23765 388.845 - 64.07109 383.252 - 45.53415 382.556 - 36.16025 378.411 - 24.16626 373.997 - 34.85616 372.826 - 67.01353 372.061 - 35.37842 370.968 - 32.96336 370.797 - 43.86817 370.016 44.43216 -369.8 - 34.85945 361.026 - 21.22712 359.667 - 25.2818 356.667 - -0.35879 354.891 - 26.66204 353.229 - 5.088395 352.803 - 34.37838 348.953 - 54.34993 348.033 55.25532 -346.47 - 44.06989 345.475 - 14.06855 345.252 - 15.18537 344.451 - 21.1237 344.057 - 21.1237 344.038 - 34.6537 343.619 - -14.3415 342.693
90 - -8.55876 338.193 - 14.11249 336.228 - 48.60107 333.735 -0.47283 -331.5 - 6.288508 330.053 - 73.83271 329.246 - 45.3165 327.715 - 36.08117 326.577 - 33.26486 325.416 - 14.48757 321.571 - 15.84639 312.307 44.29212 -307.9 - -10.0109 302.157 32.19545 -301.54 - 24.50729 296.935 - 14.54065 295.483 - 45.01959 290.647 - 15.25878 288.069 - 12.81993 283.778 - 7.486972 273.293 - 7.398556 273.119 - 26.22527 272.902 - 12.97296 272.838 - -1.19078 268.226 - -17.8569 267.895 - -8.24647 265.001 - 24.99733 264.793 - 13.58181 262.691 - 6.993088 262.091
91 - 25.10845 260.814 66.27728 -259.19 - 13.63709 258.412 - 14.71089 258.299 36.19558 -255.22 - 23.68519 250.629 - 14.10425 249.856 14.88608 -249.31 - 15.27013 244.209 - -5.95425 240.189 - -9.71384 238.957 -6.3253 -236.17 - 15.34207 234.726 - 6.303518 230.476 -13.2047 -216.52 - 17.00842 205.805 - -2.43263 205.256 - 15.29942 203.343 -12.6815 -202.79 - 33.5409 201.305 - 64.96184 200.459 - -14.1949 198.336 - 25.13719 196.653 -12.0795 -196.28 - -16.7551 191.997 - 55.3106 191.843 - 45.91015 184.755 -12.6782 -184.37 15.33914 -182.62 -13.6484 -181.82 - -24.7224 180.567 - -19.2878 179.907 0.942004 -
92 178.213 - -13.2635 177.818 - 65.41838 176.922 - -12.0291 175.827 - 35.35663 174.657 - -24.878 174.597 24.7665 -171.07 - -12.409 166.027 - 15.3093 165.873 - 56.09445 161.789 -5.71371 -160.69 - -0.65717 158.843 - -11.2165 155.325 - 36.11741 154.178 - -14.1348 153.605 - -24.6336 153.502 - -10.108 148.984 - 15.20752 144.235 - 7.379702 142.973 - 2.379905 138.992 - -16.3258 133.625 - -24.7345 132.359 - 13.96842 129.455 - 5.794258 120.213 - -22.8594 117.128 5.189442 -116.24 - -24.755 114.711 - -0.41792 114.274 - -0.68408 114.135 -1.1862 -111.31
93 - 9.256936 109.922 - 5.904457 109.518 - -23.7769 109.204 - 4.572545 107.255 7.287259 -107.16 - -24.7508 106.836 - -0.04009 82.5469 - 5.919834 82.4253
Table 2.. Spread sheet layout of DEC prime unit and correction
Dec vs Dec Corr
0 -40 -20 0 20 40 60 80 100
-100
-200
-300 Dec Corr
Dec Corr Arcseconds
-400
-500
-600 Dec
fig 28. Scatter plot of DEC prime unit v correction
94 8.3 ASSESSMENT OF POINTING MODEL SCATTER PLOTS There is an obvious trend in both HA and Dec. The fact that this is not a clean straight line suggests that there is misalignment on the Polar axis of the Telescope.
If the HA line was non-zero but horizontal, it would suggest an encoder offset or a clock error. However, as it is sloped, it indicates an alignment problem. A constant but horizontal Dec error would suggest an encoder offset. The slope indicates an altitude error in the Polar axis.
Combining the above observations, a correct re-alignment of the axis should improve the long duration exposure performance of the instrument.
95 CHAPTER 9 - CONCLUSIONS AND FUTURE WORK
9.1 CURRENT PERFORMANCE
At the time of writing, the UWS 24 inch telescope was functioning as a versatile automated research and educational tool. The majority of the original design goals and performance parameters have been either met or exceeded. One exception to this relates to its roboticism. As part of the introduction to this Thesis (page 1) it was stated that one of the final design goals was to have the telescope robotically controlled over the internet by a distant observer. Certain policy changes at UWS meant that this final stage was not completed, in a permanent sense, at the time of writing. However, some robotic experiments have been made and some internet remote delivery of images has been undertaken.
9.2 FUTURE WORK 9.2.1 The video system. The manual video assignment system has proven to be troublesome due to the large number of sources and destinations available within the observatory. The colour code system worked satisfactorily for those who were familiar with the system and well practiced with using it, but seemed unmanageable by infrequent users, particularly those with limited technical experience. To overcome this problem a microprocessor controlled video routing matrix needs to be installed. Preferably it would be of the type where each destination has a control panel from which the desired video source can be selected e.g. a row of ten push button switches marked CAM 1, CAM 2, MOON CAM etc. Using this type of system, if a lecturer needs to display moon cam through the video projector in the lecture theatre he would go to the selector panel adjacent to the projector and hit ‘moon cam’. This type of system also obviates the need for operators to return the system to a default condition.
96 A further enhancement would be the inclusion of a ‘salvo take’ function whereby a frequent user could set up the complete matrix to his standard configuration with one or two key strokes.
9.2.2. Robotics. The UWS telescope is currently able to be remotely controlled over the net by a distant observer. Processes such as image download, viewing session scheduling and prioritising, automated billing for viewing sessions, and automated logging still need to be addressed to lift the facility to its fullest potential as both a viable entity and scientific tool.
97
REFERENCES
Allen, C.J., 1973 Astrophysical Quantities, University of London, Althone Press. Bok, B.J.,1955 Size and Type of the Telescope for a Photoelectric Observatory, the Astronomical Journal, 5:27 Baruch, J.E.F.,1992 Robots in Astronomy, Vistas in Astronomy 35. Boyce, J.S.,1998 Servo Statistics, R.S. Data Library, RS Components Ltd, Northants UK. di Cicco, D., 1992 The ST-6 CCD Imaging Camera, Sky and Telescope, October , p395. Dynaserve Corp.,2003 Dynaserv Installation Manual, California, USA. Elliott, K.H., and Eyles, C.J.,1987 The University Telescope and Observatory, Journal of the British Interplanetary Society, v.40, p195-200. Genet, Russell M., Hayes Donald S., et all,1998. Robotic Observatories:a Handbook of Remote Access, Personal Computer Astronomy. Autoscope Corp., Mesa, Arizona. King, H.C.,1955 The History of the Telescope, Sky Publishing Corporation, Cambridge, Massachusetts. Levy, V., James, G., Halim, Z., & Baruch, J.E.F.,1993 The Development of Inspiration in the Classroom, In Press. Maran, S.P.,1967 Telescopes and Automation, Science 158, p867-871. Martin, R., and Hartley, K.,1985 Remote Observation of Telescopes from the United Kingdom, Vistas in Astronomy 28, p555-560. Max, Claire,2003 Adaptive Optics for Extremely Large Telescopes, UC Santa Cruz. McConnell, Anita,1992 Instrument Makers of the World, Troughton and Simms, York. Mitchell, E.W.J.,1989 A Plan for Research in Astronomy and Planetary Science by Ground Based Techniques, Serc Swindon I.S.B.N. 1-870669-10-X. Reddish, V.C.,1966 Sky and Telescope 32: 27 Ridpath, I. (Ed.) 1991 Norton’s 2000.0 (18th edition) Bath Press. Trueblood, Mark and Gennett, Russell, 1985 Microcomputer Control of Telescopes, Willman-Bell, Richmond, Virginia.
98 APPENDIX “A”. ACE CONTROL SYSTEM EXTRACTS
System Overview.
The control system utilizes two computers, one called TELSECOPE and one called CAMERA. The camera can either be operated in stand-alone mode or, preferably, through the telescope computer.
This manual described the ACE Control System software which controls the telescope, observatory, and cameras.
The computers should be left powered up so that remote access is available to the system at all times.
Remote access is available through vnc (Virtual Networked Computers) and a free version can be downloaded to your computer (www.realvnc.com). Your remote computer can be a Windows®, Linux or SunOS® workstation.
.
Logging onto ACE.
A user name and password are required to log onto ACE.
There are three levels of User access.
User Level Typical User Comment 1 Minimal Access Suitable for student / public access 2 Standard Unable to build a new pointing model and other
99 Observer engineering functions. This should be the normal observing level. 3 System Engineer Full access to engineering system functions. This level restricted to a few fully trained staff.
The Observatory Manager will issue users with a Logon name and password. When you have finished using the telescope please log out (using the menu User->Logout).
Please note that this is a dedicated telescope control computer. Users are not expected to play computer games, download music, etc., which can slow down the computer and interfere with the telescope controller. Please use your own computer for such activities!
100 The ACE main window.
The background of the main window is split into three logical areas.
The left side of the screen shows the current status of the DOME and TELESCOPE .
Many of the fields are color coded according to a standard traffic light where:
RED = STOP Something is stopped, closed, or not ready. YELLOW = Something is about to change or at a home position CHANGE GREEN = GO Ready. All boxes should be green (or yellow) when observing
Therefore, one can tell at a glance that the dome and the telescope tracking are not ready in the window below:
101
The right side of the screen shows the position of the telescope and various clocks. All this information is written to the image FITS headers together with a host of observatory and instrument settings.
102 Object Acquisition
The center part of the screen deals with object acquisition.
To open a catalog right-click the mouse anywhere on the screen to access a pop-up menu:
Select Open database and chose either a standard or custom catalog. ACE_BSC5.cat is a modified copy of the Yale Bright Star Catalog version 5.
103
Scroll through the database then select the desired object by double-clicking on the object name. This will load the object into the green entry boxes denoting a (RA, DEC) coordinate system.
The database fields can be sorted (in ascending or descending order) by clicking on the desired header.
The bright star catalog defaults to being sorted by magnitude. If, for some reason, you wanted to have a catalog default to being listed in ascending order of declination simply sort the file that way and save it. The next time it is loaded it will list in that sort order. Database Filtering
104 To filter a catalog right-click the mouse anywhere on the screen to access a pop-up menu:
In the example below all objects greater than RA 22h30m and less than RA 06h00 will be selected.
If the database is saved with the filter applied then only those objects that pass through the filter will be saved. This is a convenient way to make sub-catalogs. Save the database using the pop-up menu.
105 NOTES
106 Objects can also be entered manually using the keyboard. Click on the 0 button to clear the fields. This will place the cursor in the Name box. If the name box is left empty the control system will assign the name (RA, DEC) with values according to those fields. Data can also be sent to ACE from any ASCOM enabled application, such as Megastar, TheSky, Computer Aided Astrometry (for NEO searches) and similar commercial software packages. ACE offers a Robot Extension which permits pre-scripted observations with automated observatory open / close procedures.
Data can be entered as RA(HH MM SS.s or HH MM.m) and DEC (DD MM SS.s or DD MM.m).
However, upon pressing the GoTo button the system will check data entry and convert to the standard format for saving in the catalog. The ACE system automatically checks data entry as it is typed, to prevent incorrect input.
107
Three different Style Tabs are available, R.A., Offset and H.A.
The R.A. tab has green colored entry boxes and is the default setting.
108 The Offset tab has yellow colored entry boxes with red text.
Offsets can be in arc_seconds or in (seconds of time, arcseconds).
The H.A. tab has orange colored entry boxes. Moves in this mode park the telescope at the desired position and turn the drives off.
One the data has been successfully entered click on the GoTo to move the telescope. A confirmation dialog is issued, the appearance and color coding changing depending on the style tab.
109
110 When the telescope starts to slew to the object the GoTo button is replaced by a CANCEL MOVE button and a pair of progress bars (denoting H.A., DEC) that report how far the telescope has left to move.
Finally, there is a series of up to three “Most Recently Observed” buttons for each tab field. In the example above there is only one button as this was the first move of the night.
Simply double-click on the button to re-send the telescope back to that object.
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112 MENUS
The menus and the associated toolbars give access to a host of other services. The menus vary depending upon factors such as the User Level, the equipment installed, and the type of telescope.
The User menu
Allows user LogOn and LogOff and exit of the application. At the end of an observing session the user should LogOff. Alternatively, LogOff and exit ACE. Either of these operations will turn power off to all the motors and leave the system in a safe storage condition.
The Setup Menu is primarily used by the SystemEngineer and is discussed in Appendix A.
The Observatory Menu
If a weather station is installed the current data can be displayed using this menu.
The Dome Menu
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The dome looks after itself if AutoDome is selected. The status boxes on the main screen turn green.
To manually control the dome the following functions are available:
DomeöHome
To moving the dome past the home sensor will reset the encoder azimuth. To go past home and reset use HOME AZIMUTH. To place the dome at the sensor use PRECISE SEEK ON DOME SENSOR which will taken longer to complete.
DomeöAzimuth
To manually move the dome to a specified azimuth enter the value in this dialog.
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DomeöReset Encoder
This dialog should not have to be used. If there is a problem with the azimuth encoding simply pass home. The system remembers all data even during a power loss.
Please note that if the dome is on the home sensor this dialog will have no effect because the dome azimuth is reset to home when at home.
DomeöOpen Shutter DomeöClose Shutter
The Open and Close functions permit one or both doors to be operated.
When opening the main shutter must be fully opened before the lower shutter can be operated.
When closing the lower door must be fully closed before the main shutter can be operated.
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DomeöSmartDome
When used in conjunction with an ACE SmartDome™ the software constantly polls the status of the SmartDome™. In the event of a prolonged communications failure the some will automatically close. It will also automatically close if the rain-snow sensors are enabled and activated.
116 The Telescope Menu
Access these functions from the Menu or from the Toolbar.
TelescopeöSoftPaddle…
Displays the ACE SoftPad™ which is a screen-based hand paddle. The physical hand paddle reads the software paddle settings.
There are three fundamental settings in the hand paddle, called Guide, Set, and slew. For safety reasons slew is only available
117 with the physical hand paddle, located in the dome, or by using the GoTo button in the main ACE software window.
The settings are adjustable by the System Engineer, and are typically 1 to 25 arc_seconds/second for guide and 50 to 1000 arc_seconds/seconds for guide. Use the slide bars to select the desired guide and set speeds. If you always want to use the same settings the Lock button will simplify the dialog.
The four black buttons represent the cardinal directions N, S, E, W. It is also possible to select two-axis moves, NW, NE, SE, SW. Simply press and hold down the left mouse button over the desired button. Moving the mouse over a different button will automatically change to that direction. The current direction is shown in the box located at the center of the black buttons.
The telescope focus has similar settings, called fine, coarse and slew. The focus value is displayed in several locations including at the bottom of the hand paddle.
Finally, the slider bar at the top of the dialog is used to adjust the slew speed of the physical hand paddle. Most observers cannot react as quickly as the computer and so the slew speed of the telescope can be changed from 20% to 100% of the computer slew speed, with 80-% being the default.
118 TelescopeöZenith Park TelescopeöStow Telescope TelescopeöDomeFlatPark
The park utilities all have the same properties, namely moving the telescope to a fixed (HA,DEC) and turning off the drives.
Zenith Park is used before closing the mirror petals on the Pomona Telescope because this telescope has a special condition that the petals can only be opened or closed when within 5 degrees of the zenith.
Stow Telescope is used to park at some other pre-determined position. This might be required for filling a dewar, etc.
DomeFlatPark is used to align the telescope so it is pointing at the flat field screen, positions the dome at the correct azimuth, and opens the mirror petals.
TelescopeöOpenMirrorCover TelescopeöCloseMirrorCover
Special case for Pomona Telescope where the telescope must be at an altitude > 85° for the covers to open. All other telescopes can open without restriction. Typical open / close time < 15 seconds.
TelescopeöResetEncoders
For use on telescopes with incremental encoders.
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Software limits resetting to (RA, DEC) when tracking or (HA, DEC) when not tracking. If the encoders are reset by more than 1 degree then a warning is issued before resetting.
The coordinates are picked up from the last GoTo move but can be edited if necessary.
Under normal circumstances you should not have to reset the encoders. Check the pointing model is turned on and that there are sufficient grid points in the model. If not add the current knbown position to the model.
120 TelescopeöFocus
The telescope focus tool is another floating dialog that can be used to move the focus ram to pre- selected positions.
The current focus is read out at the top of the box.
Pressing the Go To Focus button will move the ram to the absolute value shown in the green edit box.
For telescopes with multiple instruments up to four pre-determined values can be stored, and named, using the Setup function. In this example there are four instruments called S2KB, Moasaic, Eyepiece, and Port 4. Pressing on one of these buttons will load the preset value into the green edit box.
AutoFocus is for cameras connected to the ACE Control system and permits automated focus adjustments.
Incremental manual focus adjustments can be made using Jog+ and Jog- buttons which moves the ram by the number of counts entered in the yellow box.
Drive to Zero moves the ram all the way out (maximum distance between mirrors) and resets the encoder to zero. Drive to Max moves all the way to the maximum focus limit. STOP can be used to quit motion when the telescope is almost in focus. The Backlash button is used to remove lead-screw backlash. Servo is used to keep the focus ram at the same counts as the telescope moves. It is currently only used at a retrofit telescope at Kitt Peak National Observatory.
121 Change With Filters allows the focus ram to be automatically moved as the filters are changed. Once a given filter has been focused use the Bias button to set the filter zero- point. Then use the Filter Offset button to establish offsets for the other filters when they are in focus. This procedure only needs to be performed each time new filters are installed.
TelescopeöTrackEnable
Toggles the tracking on/off.
A warning is issued.
122 TelescopeöTrackRates
The telescope track rates can be changed using this dialog.
Nominal values are 15.0000 ±3.0000 arc_seconds/sidereal second but larger values can be entered if so desired.
In declination the nominal rate is 0.0000 ±3.0000 arc_s/s.
Again the rate can be increased by the System Engineer (it is set at this nominal rate to prevent large data entry errors).
Custom rates can be saved for later retrieval.
Finally, it is possible to superimpose Solar System rates. Enter the rates of the NEO or other object and these will be added to the base tracking rates.
The Track Enable button will change the tracking state if it is currently different to the requested value.
TelescopeöCenter CCD
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Used in conjunction with the CCD Camera Interface. The user clicks the mouse on the desired object to be centered. That (X, Y) value is entered into the edit box. Pressing Center Star will move the telescope to place that object at the center of the CCD.
The Setup button expands the dialog for changing the basic scaling parameters . Up to two different CCD’s can be stored.
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The Instruments Menu will vary depending on the current equipment installed.
InstrumentsöFilterWheel
The ACE Dual wheel has two stacked wheels so in most circumstances, to observe through just one filter, the un-used wheel is set to the empty position. Up to four wheels are currently accommodated.
125 The Video Cameras permits up to eight cameras to be switched and either a single camera, the first four cameras, or the last four cameras to be displayed. It addition it is possible to turn on low-wattage camera lights.
ObservationsöSetup; ObservationsöSimple; ObservationsöSequence
Use the setup menu to put in the observer names and any temporary notes like “non- photometric”.
Then select the directory and name structure for the images. The image numbers are automatically incremented.
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Take single exposures using the Simple dialog
Real-time feedback is available. The report box changes color where yellow is idle, green is exposing and the image will be saved, and red is exposing and the image is not saved.
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When the system is not in auto- save mode the SAVE button becomes available. You can save an image at any time.
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Finally, for sequences it is possible to have multiple filter observations. Sequences can be saved or recalled. Variable or fixed binning permits a complex set of observations to be taken.
The observatory can be closed after the observations are completed.
For more complex observations requiring multiple objects through multiple filters the ACE Robotic Control extensions are used. The ACE telescope has a robotic library which is ASCOM compatible.
129 Appendix A: System Engineer and the Setup Menu
The System Engineer is able to change the fundamental operating parameters of the telescope. Access to these functions are password protected and only fully trained persons should attempt to alter parameters. If there is a problem with the setup parameters please contact ACE for assistance before making changes.
The number of menus that appear depends on the User Level. The appearance for a normal observer is shown below.
130 SetupöEngineering Services…
Prevents a remote user from operating the system when the telescope is being serviced.
It is also possible to set the hand paddle velocities to a fractional custom level so the operator can limit the maximum slew rate while operating overhead cranes, etc, during instrument changes or top-end secondary changes.
Press Exit Engineering Services to exit the dialog.
SetupöSystem Parameters…
This menu gives access to a complex series of tabbed dialogs to set fundamental parameters of the telescope, such as longitude, latitude, encoder ratios, and other features which the regular user cannot change.
The menu is password protected and brings up the following dialog:
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The contents of the setup dialogs are shown here for reference only. Complete details are in the Technical Reference Manual. Some information is taken from these files and written to the image FITS headers.
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The values in the ACE SoftPad™ are also read by the physical hand paddle.
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Mirror Cover Park was designed for telescopes without automated covers. For telescopes with fully automated covers the option does not appear in the telescope park
135 menu. Flat Field Park is for aligning the telescope and dome with a calibration screen. Stow Telescope is for a standard home position.
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The software handles an offset-axis telescope and the telescope being offset from the dome center.
137 If the DAYLIGHT SAVINGS field is left empty the system will always report standard time.
This dialog controls access to the setup menus and enables or disables the User Logon feature.
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This dialog is used with telescopes having incremental on-axis encoders. It is not used for absolute encoders systems.
139 SetupöEquipment Installed…
Another password-protected series of tabbed dialogs that with auxiliary instrumentation. Only those dialogs relevant to your system are shown here.
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141 SetupöControlCardöVersion
Reports the revision number of the telescope motion control card.
SetupöControlCardöControl Card Diagnostics
The first dialog, AXES PARAMETERS, reports low-level motor and encoders counters registers, limit switches, home sensors, current velocity, direction and other card parameters. Used by the System Engineer as a diagnostic tool.
The second dialog, Control InOut, reports the low-level status of the digital i/o bits. The Names button permits customization to suit the hardware installed.
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143 SetupöControlCardöAbsolute Encoders
This is another diagnostic tool. It shows the absolute encoder counts. The encoders have 8192 pulses per revolution and up to 4096 revolutions. Image capture shows the H.A worm at 5300 pulses on rotation number 12. Telescope is therefore in the west (positive rotation) at 95412 total counts and declination is North by 174811 counts. The H.A. worm is 5300/8192 of the way through its rotation. This can be used to map out periodic errors.
The zeropoints should be at 0. If not, press ResetZeropoints.
When the telescope is tracking the HourAngle encoder should be constantly increasing. This tool is a easy way to check encoder functionality.
The ACEFlex™ Pointing Model.
The ACE Control System uses a grid map to determine the pointing corrections. This has distinct advantages to alternative methods based on mechanical and optical modeling of the telescope. First, he grid point method is independent of the telescope and hence the same technique can be used for all telescopes. Second, the grid point model is able to learn in real time and as more points are added the system is capable of extremely high accuracy.
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The ACEFlex™ pointing model uses a series of grid points, fixed in (HA, DEC) or (AZ, ALT), which are randomly scattered around the sky. Although the positions of the grid points is random, a spacing of about 5 degrees on average, around the whole sky, will yield optimal results. Corrections are stored for each grid point and the model takes into account mechanical mount flexure, tube flexure, bearing errors, polar misalignment errors and refraction as a function of temperature and atmospheric pressure.
Depending on the grid density and the position of the target a 1, 2, 3 or 4 neighboring grid points will be used in the model. Under normal circumstances 5 neighbors are used.
How to apply a Pointing Model.
You must have a sufficient User Level privileges to apply a model. Otherwise the menu option will not be available.
SetupöACEFlex Pointing ModelöApply Model displays the following dialog:
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Under normal circumstances the user does not need to enter this dialog. It is possible to select different models depending on the instrumentation installed. Also, as more points are added to the grid it becomes more efficient to decrease the search radius around the target star. A distance-weighted solution will bias the correction to apply more weight to the closer grid points. The temperature and pressure are stored for each grid point. The current temperature can either be read by the weather station (if installed) or manually entered (which is the main reason an observer might want to use this dialog). Finally, the number of elements in the ephemeris is used to calculate the position of the telescope as a function of time. If an auto-guider is used the ephemeris is ignored, otherwise the telescope positions are corrected to match the ephemeris.
146 How to create a Pointing Model.
You must have a sufficient User Level privileges to create a model. Otherwise the menu option will not be available.
SetupöACEFlex Pointing ModelöApply Model displays the following tabbed dialogs:
The Grid Point Selector is used to find suitable grid-point stars. To use this dialog first open a catalog using the Pointing Map Star Catalog button. The catalog ACE_BSC5 should be used. This is a formatted copy of the Yale Bright Star Catalog #5. The name of the catalog appears in the green edit box.
Next select a candidate grid point in terms of (HA, DEC) or (Az, Alt). For an equatorial telescope we suggest using (HA, DEC) and when building the model to make rasters in HA at different declination bands, typically, 0, 10, 20, 30, etc and then come back and fill in at band 5, 15, 25, etc.
The screen capture shows a selection at (HA=4, DEC=30) using all stars down to 8th magnitude within a radius of 5 degrees of the grid point. A total of 19 stars were found. The stars are then listed in magnitude order. To select by distance from the grid point
147 select the Angle header. Double-click on the desired star name and the selection will appear at the right side. Warning: Clicking on the GoTo button will move the telescope without further prompting. As you have System Engineer status we assume that you know what you are doing and have removed “annoying” reminder dialogs.
Once the telescope has arrived at the destination take an image, then use TelescopeöCenterCCD to calculate the residual correction. Once the telescope has been centered it is time to save the grid point.
Click on the ACEFlexDatabase tab to select the other tabbed dialog. If a flex map is not open click on Open FlexMap to open an existing file or create a new one. The name of the catalog appears in the green edit box. Then use the Star Centered? Click to ADD button to add the new grid point. Grid points have a unique ID based on the U.T. Date and the UT Time. To remove a grid point highlight that point and click on the Delete button. The total number of grid points is also shown.
The database also keeps track of the current observer so that points can be removed based on date, observer and other parameters.
A screen capture showing the construction of a pointing model.
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