Building a Solar Projection Box

Appendix A

As discussed in Chap. 2 , a projection box offers some distinct advantages for the solar observer. It allows the Sun’s image to be viewed safely without the inconvenience of having to hold a screen behind the telescope. It leaves your hands free to make notes, drawings and adjustments. It is much easier to make accurate records of sunspot positions with a projected image than it is by looking directly at the Sun through a fi lter. If a projection box is attached to the telescope, the telescope’s fi eld of view does not move relative to the projection screen, and sunspots and other solar features can be observed and recorded very accurately. A projection box also allows the Sun to be observed by groups of people and, if thoughtfully constructed, can prevent curious children from putting their heads to the eyepiece (or at least make it very dif fi cult!). The projection box described here was built entirely from 6.4 mm (1/4 in.) thick balsa wood bought from an art and crafts store. The interior of the box was lined with thin black card (also obtainable from art stores) in order to reduce internal re fl ections, which can spoil the contrast of the image. Two sides of the box are parallel, so that the pieces could be joined together easily using balsa wood framing of square cross-section, 12.5 mm (1/2 in.) on a side. However, the sides of the box were made so that they taper down to 75 mm (3 in.) at the eyepiece end, as other- wise the front of the box would collide with parts of the telescope tube and the whole thing would look bulky and ungainly. Note that because balsa wood is intended for making such things as model airplanes and other small objects and not large pieces of apparatus like projection boxes, it often comes in strips no more than 75 mm (3 in.) or 100 mm (4 in.) wide. If this is the case with your balsa wood, you will need to cut two or more pieces of wood and then glue them together. Glue all the joints using ordinary wood adhesive from a local hardware store. The most important dimension to establish when building a projection box is its length. Using an eyepiece of a given magni fi cation, moving the screen further

L. Macdonald, How to Observe the Sun Safely, Patrick Moore’s Practical Astronomy Series, 197 DOI 10.1007/978-1-4614-3825-0, © Springer Science+Business Media New York 2012 198 Appendix A behind the eyepiece increases the size of the projected image. To do serious solar work you need an eyepiece that will show the whole solar disc comfortably within the fi eld of view. Avoid using an eyepiece that barely accommodates the whole Sun and so shows the limb of the Sun’s disc very close to the edge of the fi eld, as the view at the edge of the fi eld is distorted in most eyepieces. On the other hand, using too low a power gives a very long projection distance for a good-sized disc and results in an inconveniently long projection box. An eyepiece giving a magnifi cation of between 50× and 65× gives the best results. The standard diameter used by amateur astronomers for a projected solar image is 152 mm (6 in.), although if you use a very small telescope you may fi nd a 100 mm (4 in.) disc easier to work with. To fi nd the correct length for a projection box on your own telescope, draw a circle of your chosen disc size on a sheet of plain paper. Here we will use a 152 mm (6 in.) disc size as an example. Insert your choice of projection eyepiece in the telescope so that it is not quite fully placed in the drawtube but the eyepiece barrel sticks about 3 mm out. Determining the correct projection distance for a 152 mm disc should in theory be a simple matter: just measure the distance behind the eyepiece you have to hold the paper in order for the Sun’s image to exactly fi ll the circle. You should note, however, that Earth’s orbit around the Sun is slightly elliptical, which means that Earth’s distance from the Sun varies during the course of the year. Earth is furthest from the Sun in July and closest in early January.1 For the solar observer, the upshot of this is that the Sun’s apparent diameter is slightly larger in January than it is in July. More precisely, its January diameter is 32.5 arc min, whereas in July it is just 31.5 arc min. The average between these two extremes is 32 arc min, so the variation of 0.5 arc min either way means that the diameter of the projected image varies by about 1.56 % either way, which for a 152 mm disc translates into a variation of about 2.4 mm on either side. This is enough to make the real solar image too small for a 6-in. circle in summer and too large in winter, and will compromise the accuracy of solar drawings. Therefore, you need to allow the projection distance to vary by a corresponding percentage. The easiest way to determine the maximum and minimum projection distances needed throughout the year is to simulate the variation in the Sun’s apparent diameter by drawing three concentric circles: one of your chosen disc diameter (in our case 152 mm), one of the maximum disc diameter (152 mm + 3 mm = 155 mm) and a third of the minimum diameter (152 mm − 3 mm = 149 mm). The increment has been rounded up from 2.4 to 3 mm in order to give slightly more tolerance than you actually need. You can then simply measure, and note down, the projection distance required to fi ll each circle. It is essential to measure the projection distance accurately: it is defi ned as the distance between the rear surface of the eyepiece and the surface of the projection screen . In the case of the given setup, with an 80 mm

1 This may seem paradoxical to inhabitants of the northern hemisphere, who experience winter when Earth is closest to the Sun! But the cooling of the northern hemisphere in winter caused by the tilt of Earth’s axis away from the Sun totally overwhelms the very slight heating effect caused by Earth’s closer proximity to the Sun at this time of year. Appendix A 199 refractor of focal length 910 mm projecting using a 15 mm Plössl eyepiece (magni ﬁ cation 61×), the distances were: Average 263 mm Maximum 270 mm Minimum 258 mm You need to build your box so that it allows for the maximum projection distance required. If the box is a little too long you can shorten the distance slightly, and thus get the image down to the correct size by pulling the eyepiece out a little in its drawtube, but if it is too short you cannot extend the box! The ﬁ nal length for your projection box is this distance (marked d in Fig. A.1 ) plus the distance by which the

Pipe Bracket Star Diagonal (seen from behind)

Eyepiece

6.4 mm– thick Balsa Wood d

Projection Screen

CornerJoint

Fig. A.1 Diagram showing the construction of the author’s projection box. The projection distance d determines the diameter of the projected solar image 200 Appendix A eyepiece protrudes into the box. When you use the box, you can make small changes to the projection distance to allow for the variation in the Sun’s apparent size by adjusting the position of the eyepiece in its drawtube. Inserting the eyepiece fully will give the maximum projection distance, whereas pulling it out by a few millimeters and then clamping it again will give the minimum. The screen end of the box can be square. When determining its size, allow for 5 mm of clearance around the solar disc (i.e., 5 mm on each side if measuring its cross section), plus the thickness of the square corner joints holding the box together (another 26 mm or 1 in. in total) and the thickness of the sides of the box (total 13 mm or ½ in.). For the box in the example, then, the total width of the base comes to: 152 mm+++ 5 mm 5 mm 26 mm + 13 mm = 201 mm

Thus the screen end of the box should be 201 mm square. The top piece, through the center of which the eyepiece mount should be inserted, has the same width as the tops of the side pieces (75 mm, 3 in.) and the same length as the internal width of the box (188 mm). The hole for the eyepiece or drawtube (see below) should be just wide enough for the tube to slide through with as little play as possible. If you have access to a lathe or other precision cutting device, boring a hole of the correct diameter should not be a problem. If you only have access to hand tools, you can make a very functional eyepiece hole quite easily by drawing a circle of the correct diameter in the exact center of the top piece and then drilling a series of small holes around its circumference. If the holes are spaced reasonably closely together, you can then break down the walls between them with a chisel until the central piece of wood falls out. You can ﬁ le the interior of the resulting hole smooth with sandpaper—though be careful not to make it too big for the tube. The front of the box—i.e., the side not used for looking at the Sun’s image—needs to be blocked in, preferably with more balsa wood for rigidity, or with thick black card. You now have a box with just one open side, into which you look to view the Sun’s projected image. How you attach the box to the telescope depends on the characteristics of your instrument. Ideally, the box should slide over the drawtube and be clamped either with a screw attached to a collar at the front of the box, or by making the box ﬁ t very tightly over the drawtube (e.g., by lining the eyepiece hole with felt). However, some telescopes, particularly small refractors, may not reach focus without a star diagonal. In this case, you need to slide the box over the eyepiece end of the star diagonal, so that the box’s long dimension is at right angles to the telescope tube. Clamping the box rigidly to the telescope tube requires some ingenuity if you use a star diagonal. I attached a pipe bracket (obtained from the plumbing section of a hardware store) to the top piece of the box, with a bolt passing through it and so clamping the box tightly to the eyepiece collar of the main telescope. Two smaller bolts going through the sides of the pipe bracket keep the box’s orientation steady (Figs. A.1 and A.2 ). Appendix A 201

Fig. A.2 The author’s projection box, attached to an 80 mm (3.1 in.) refractor with a pipe bracket

Using the star diagonal method of projecting the Sun’s image is probably better than direct projection, as you can better shade the interior of the box from ambient sunlight, and the near-horizontal position of the Sun’s image makes it easier to view. A disadvantage is that it projects a reversed solar image—i.e., east left, west right, which is the opposite way around from a solar image projected straight through. Orientation of the Sun’s image is discussed in more detail in Chap. 4 . To obtain the best projected images you should use a good quality, thick paper. Many amateurs over the years have used “Bristol board,” a very smooth white paper available from art shops. This gives very good results, but the thick, smooth cartridge paper with a slightly creamy tint shows sunspot detail even better. Faculae, though, are more prominent on Bristol board. You can use a sheet of Bristol board and a sheet of cartridge paper pasted together, so that you can ﬂ ip between the two surfaces to see the two types of solar features to their best advantage. To plot sunspot positions use a rotatable projection grid made of Bristol board; again, this is discussed in detail in Chap. 4 . Appendix B

Equipment Suppliers

This list is not intended to be comprehensive but rather is a selection of suppliers of solar observing equipment that amateur astronomers have found to be useful. It does not constitute a recommendation of these suppliers and neither the author nor the publisher makes any guarantee as to the safety of these products or their suit- ability for solar observing. Try to solicit the advice of an experienced solar observer before buying any piece of equipment. Suppliers of astronomical equipment exist in vast numbers. This list is restricted, therefore, to those companies selling products either speci ﬁ cally for solar observing or useful for solar work. To ﬁ nd suppliers of telescopes and other general astronomical equipment, try your favorite Internet search engine or peruse the advertise- ments in astronomy magazines (see Appendix D , “Further Reading”).

Suppliers in North America

Astro-Physics, Inc., www.astro-physics.com . Suppliers in USA of Baader Planetarium fi lters and accessories. Celestron International , www.celestron.com. Solar fi lters and accessories to suit the wide range of Celestron telescopes; also the NexImage camera, a webcam optimised for astronomy. Celestron do not sell directly to the public, but their products can be obtained through Celestron dealers worldwide. Contact Celestron to fi nd your nearest dealer. Coronado, part of Meade Instruments, www.meade.com/product_pages/coronado/coronado.php . A leading manufacturer of sub-angstrom H-alpha fi lters and

L. Macdonald, How to Observe the Sun Safely, Patrick Moore’s Practical Astronomy Series, 203 DOI 10.1007/978-1-4614-3825-0, © Springer Science+Business Media New York 2012 204 Appendix B solar telescopes for the amateur solar observer, including the Personal Solar Telescope (PST), a complete H-alpha solar telescope for just under $500. DayStar Filters LLC , www.daystar fi lters.com . The longest-running manufacturers of sub-angstrom H-alpha fi lters. Kendrick Astro Instruments , www.kendrickastro.com/astro/solar fi lters.html . Suppliers of Baader AstroSolar fi lters. Lumenera Corporation , www.lumenera.com . Top-of-the-line webcam-type cameras suitable for high-resolution solar imaging. Orion Telescopes & Binoculars , www.telescope.com. Suppliers of full-aperture glass solar fi lters for white-light observing and Coronado H-alpha telescopes; also many useful accessories, including adapters for mounting digital cameras to telescopes. Point Grey Research , www.ptgrey.com/products/ fl ea3/ fl ea3_ fi rewire_camera. asp. Suppliers of the tiny, but highly effective, Flea3 webcam-type camera suitable for high-resolution solar imaging. Thousand Oaks Optical , www.thousandoaksoptical.com. Manufacturers of both glass and plastic white-light solar fi lters for visual observing, solar eclipse viewers, glass fi lters for solar photography and 1.5-Å H-alpha prominence fi lters.

Suppliers in the UK and Europe

Telescope House (Broadhurst Clarkson and Fuller Ltd), www.telescopehouse.com . Suppliers of white-light solar fi lters and Coronado H-alpha fi lters and telescopes. Baader Planetarium , www.baader-planetarium.com. Manufacturers of Baader AstroSolar Safety Film and AstroSolar Photo Film Mylar-type aperture fi lters, also many other fi lters and accessories for solar observing—e.g. the “Fringe-Killer” fi lter. David Hinds Ltd , www.dhinds.co.uk. UK suppliers of Baader Planetarium equipment; also of telescopes and accessories by Celestron. See the two separate websites: www.celestron.uk.com and www.baader-planetarium.uk.com . The Imaging Source , www.theimagingsource.com/en_US. Manufacturers of advanced webcam-type cameras for high-resolution imaging. Lunt Solar Systems , www.lunt-solarsystems.eu . Manufacturers of a wide range of H-alpha and Ca-K solar telescopes and fi lter systems. SCS Astro , www.scsastro.co.uk . Solar fi lters, including DayStar fi lters. Solarscope , www.solarscope.co.uk. Manufacturers of high-end H-alpha solar fi lters and telescopes. The Widescreen Centre , www.widescreen-centre.co.uk . UK suppliers of Lunt solar fi lters and telescopes. Appendix C

Solar Observing Organizations

Astronomy Clubs

If you are new to solar observing, and certainly if you are starting out in astronomy, the ﬁ rst place you should go for advice on observing is your nearest local astronomy club or society. There are bound to be some members there with experience of solar observing and most are willing to provide help and encouragement as well as advice on what equipment to buy. If you cannot ﬁ nd a local society in your area, try contacting the following national organizations of astronomy clubs: (In the USA): The Astronomical League, www.astroleague.org/ , maintains a list of local astronomy clubs and their contact details. The monthly magazine Sky & Telescope (see also under “Magazines” in Appendix D ) has a web page that allows you to search for astronomy clubs (and also museums, observatories and planetari- ums) in your area: http://www.skyandtelescope.com/community/organizations . (In the UK): The Federation of Astronomical Societies (FAS) , http://www. fedastro.org.uk/fas/, maintains a list of local societies that are members of the FAS, including their websites and details of their meetings.

National Organizations in the United States

The Solar Section of the American Association of Variable Star Observers , www.aavso.org/solar , focuses on determining the American Relative Sunspot

Number (R A ) using sunspot counts supplied by contributing members.

L. Macdonald, How to Observe the Sun Safely, Patrick Moore’s Practical Astronomy Series, 205 DOI 10.1007/978-1-4614-3825-0, © Springer Science+Business Media New York 2012 206 Appendix C

The Association of Lunar and Planetary Observers , http://alpo-astronomy. org/ , also has a Solar Section which emphasizes recording solar activity pictori- ally—by drawings and electronic imaging. Royal Astronomical Society of Canada , www.rasc.ca. Publishes the very useful annual Observer’s Handbook .

National Organizations in the UK

The leading association of amateur astronomers in Great Britain is the British Astronomical Association , www.britastro.org. The BAA has a very active Solar Section, to which several dozen members send monthly observations. You can access its website through the BAA home page above. If you are new to solar observing you may wish to consider joining the Society for Popular Astronomy , www.popastro.com. The SPA is a national society for beginning and intermediate amateur astronomers of all ages. It has a very active Solar Section that helps beginners master the basic techniques of solar observing. The SPA also publishes a lively bimonthly magazine, Popular Astronomy; in this, the Solar Section publishes regular reports based on observations sent in by members. Appendix D

Further Reading

Books on the Sun and Solar Observing

BECK, R. et al., Solar Astronomy Handbook (Willmann-Bell, 1995). A very detailed compendium of amateur methods of observing and imaging the Sun, cov- ering a number of technical topics not described in this book, including observing the Sun at radio wavelengths. Rather dated now, but a good reference for the more advanced solar observer. GOLUB, L. and PASACHOFF, J. M., Nearest Star: the surprising science of our sun (Harvard University Press, 2001). An easy-to-read guide to how the Sun works. JENKINS, J. L., The Sun and How to Observe It (Springer-Verlag, 2009). A technical guide to observing and imaging the Sun. LANG, K. R., Sun, Earth and Sky (2nd edition, Springer-Verlag, 2006). A guide to our current knowledge of the Sun and its in ﬂ uence on Earth. LANG, K. R., The Cambridge Encyclopaedia of the Sun (Cambridge University Press, 2001). A beautifully-illustrated guide to our nearest star. It describes the workings of the Sun to a quite high technical level, although mathematics are pre- sented separately in text boxes and so do not interrupt the ﬂ ow of the narrative. MOBBERLEY, M., Lunar and Planetary Webcam User’s Guide (Springer- Verlag, 2006). An introduction to webcam imaging; includes a chapter on imaging the Sun with a webcam. PHILLIPS, K. J. H., Guide to the Sun (Cambridge University Press, 1992). An accessible but detailed guide to the Sun and how it works.

L. Macdonald, How to Observe the Sun Safely, Patrick Moore’s Practical Astronomy Series, 207 DOI 10.1007/978-1-4614-3825-0, © Springer Science+Business Media New York 2012 208 Appendix D

PUGH, P., Observing the Sun with Coronado TM Telescopes (Springer-Verlag, 2007). A survey of the various solar telescopes, ﬁ lters and accessories that were available at the time of the book’s publication. TAYLOR, P. O., Observing the Sun (Cambridge University Press, 1991). A detailed guide to monitoring solar activity by sunspot counting and electronic methods.

Books on Photography and Digital Imaging

BERRY, R., and BURNELL, J., The Handbook of Astronomical Image Processing , 2nd Edition (Willmann-Bell, Inc., 2004). A detailed guide to image processing, with a companion CD-ROM containing AIP4WIN image processing software. COVINGTON, M. A., Astrophotography for the Amateur (2nd Edition, Cambridge University Press, 1999). A detailed guide to all aspects of amateur astrophotography. COVINGTON, M. A., Digital SLR Astrophotography (Cambridge University Press, 2007). A specialised guide to astrophotography techniques with DSLR cameras. Contains some very brief notes on webcam imaging. DRAGESCO, J., High Resolution Astrophotography (translated by Richard McKim, Cambridge University Press, 1995). A “classic” from the 35 mm ﬁ lm era, this book is nevertheless essential reading for the serious solar observer and imager today, for it includes thorough technical discussions on resolution, seeing condi- tions, observing sites, telescopes and accessories—all as important in the digital age as they were in the age of ﬁ lm. IRELAND, R. S., Photoshop Astronomy (2nd edition, Willmann-Bell, Inc.). A detailed guide to astronomical image processing using Adobe Photoshop . Comes with a companion DVD. REEVES, R., Introduction to Digital Astrophotography: Imaging the Universe with a Digital Camera (Willmann-Bell, Inc., 2005). A superb guide to imaging with digital cameras. It covers compact digital cameras as well as DSLRs and has a strong chapter on webcam imaging. REEVES, R., Introduction to Webcam Astrophotography: Imaging the Universe with the amazing, affordable webcam (Willmann-Bell, Inc.). A book devoted to webcam imaging, by the author of Introduction to Digital Astrophotography (above).

Reference Books

The Handbook of the British Astronomical Association is published annually by the British Astronomical Association (Burlington House, Piccadilly, London). It contains detailed solar data, including P , B0 and L0 (essential for working out solar co-ordinates) tabulated at 5-day intervals. See Appendix B for more about the British Astronomical Association. Appendix D 209

The Astronomical Almanac is also published annually and is a collaboration between Her Majesty’s Stationery Ofﬁ ce in the UK and the United States Naval Observatory. It is available in both countries from astronomy book suppliers. The

Almanac tabulates P , B0 and L 0 at daily intervals. Willmann-Bell, Inc. also publishes a software version of the Almanac known as the Multiyear Interactive Computer Almanac 1800–2050 .

Magazines

The major commercial astronomy magazines often contain articles on solar observing and the latest developments in our understanding of the Sun. If you are a serious solar observer (or a serious amateur astronomer of any kind), it is a good idea to get at least one magazine regularly, as they often present information that is more up- to-date than in books. Sky and Telescope ( www.skyandtelescope.com/ ) contains many “how to” observing articles. Astronomy ( www.astronomy.com/ ) also has many articles on practical astronomy. Both magazines can often be found in British newsagents as well. In the United Kingdom, Astronomy Now ( www.astronomynow.com/ ) and Sky At Night ( www.skyatnightmagazine.com/ ), published by the BBC, are both available from many British newsagents. Both are very strong on equipment reviews.

Websites

The following websites may be of use to the solar observer: Current Solar Images From Earth Big Bear Solar Observatory: http://www.bbso.njit.edu/ Mount Wilson Observatory: http://www.mtwilson.edu/sci.php Uccle Solar Equatorial Table (images from Europe): http://sidc.oma.be/uset/ index.php Current Solar Images From Space SOHO spacecraft: http://sohowww.nascom.nasa.gov/ Solar Dynamics Observatory: http://sdo.gsfc.nasa.gov/ STEREO spacecraft: http://stereo.gsfc.nasa.gov/ Solar Activity, Space Weather and Aurora Warnings Current solar activity and space weather: http://spaceweather.com/ (also includes other astronomical images sent in by viewers). Space Weather Prediction Center: http://www.swpc.noaa.gov/ Current solar active regions with ofﬁ cial AR numbers: http://www.nwra.com/ spawx/listsrs.html 210 Appendix D

Solar Position Measurements Peter Meadows’s website (UK)—Stonyhurst discs and software for determining heliographic coordinates: www.petermeadows.com

TiltingSun—software for determining P , B0 and L0 and showing the Sun’s current tilt and orientation: http://www.atoptics.co.uk/tiltsun.htm

Current values of P , B0 and L 0 : http://www.jgiesen.de/sunrot/index.html Sunspot Numbers Solar Inﬂ uences Data Analysis Center (SIDC)— http://sidc.oma.be/ . Publishes the ofﬁ cial Relative Sunspot Number, in continuation of the Relative Sunspot Number begun by Rudolf Wolf in 1848. American Association of Variable Star Observers (AAVSO)—Solar Section— http://www.aavso.org/solar . Issues a monthly electronic Solar Bulletin that

publishes the American Sunspot Number—R A . Index

A C Active areas , 84–88, 90, 91, 93, 94, 103, 128 Cable release , 144, 155, 157, 164 Active prominences , 125–127 Ca-K. See Calcium-K Active regions , 9–11, 55, 59, 79, 105, 115, Calcium-K , 62, 102, 124–125 118, 125–127, 130, 131, 182 Camera adapters , 148, 150, 154, 157, 158, 168 Adapters (for cameras) , 143, 150, 154, 168 Cameras Adobe Photoshop , 187, 193, 194, 196 CCD , 63, 123, 137, 138, 145, 169, 177, Adobe Photoshop Elements , 187–189, 178, 194 193–196 digital compact , 137–144, 146, 148, 151, Afocal method (photography) , 151, 164, 168, 162–165, 168–170, 173, 175, 176, 169, 190 178, 184, 186, 188, 192 Alt-azimuth mountings , 25, 26, 69, 135 digital SLR , 103, 141–144, 164 Aperture ﬁ lters , 24, 25, 32, 33, 35–37, 45, 98, webcam-type , 21, 169, 176, 178, 198 146, 152, 156, 163, 168, 180 Carrington, R. , 61, 70 Aurorae , 13, 14, 55, 61 Catadioptric telescopes , 22, 24–27, Autofocus , 163, 166 35–37, 145 Automatic exposure , 141, 162 Central meridian , 74, 76–78 Chromosphere , 5, 6, 9, 10, 22, 101–134, 168–172, 181 B CMEs. See Coronal mass ejections (CMEs)

B 0 , 73–76, 90, 97, 98 Colour (of digital image) , 194 Baader coronagraph , 119–121 Compact cameras. See Cameras Baader fi lters (white-light) , 34, 125 Compact fl ash cards. See Memory cards Baader K-line fi lter , 125 Contrast (in image processing) , 33–35, Binoculars , 37–39 38, 44, 47, 48, 52, 97, 98, 108, Bipolar sunspot group , 51, 53, 75 111, 112, 115, 117–120, 144, Brightness (in image processing) , 88, 89, 145, 150, 151, 160, 164, 168, 191–194, 196 169, 171, 183, 185, 186, Butter fl y diagram , 78, 79 188–194, 196

L. Macdonald, How to Observe the Sun Safely, Patrick Moore’s Practical Astronomy Series, 211 DOI 10.1007/978-1-4614-3825-0, © Springer Science+Business Media New York 2012 212 Index

Convective zone (of sun) , 4, 47 photographic fi lm (DANGER!) , 32, 35, Core (of sun) , 3, 43 147, 148, 168 Corona , 5, 6, 10–12, 16, 101, 103, 105, 107, smoked glass (DANGER!) , 32 119, 127, 153 in solar photography , 24, 34, 135, 137, Coronado CEMAX eyepieces , 116 145–147 Coronado fi lters , 111, 115 Flares, solar , 9, 15, 61, 105, 126, 131 Coronagraph , 6, 101, 103, 107, 108, 119–121, Flocculi , 105 171, 172, 196 Focusing (for photography) , 123, 135, 142, Coronal holes , 11, 13, 14 143, 147, 160, 164–166, 169 Coronal mass ejections (CMEs) , 11–13, Focusing magni fi ers , 142, 166 15, 16 Focusing screen (in DSLR cameras) , 164, 165, Cropping , 187, 189, 190 167, 170, 175 Fork mountings , 26 Fringe-Killer fi lter , 31, 168, 180, 194 D DayStar fi lters , 108, 109, 113, 114, 116–119, 124, 125 G Deslandres, H. , 107 Geomagnetic storms , 13–16, 134 Dobsonian mounting , 25, 151 Glass fi lters , 34, 35, 60, 145, 193 DSLR cameras. See Cameras Go To telescopes , 22, 26 Granulation, solar , 31, 47 Graphs of solar activity , 94 E Eclipse (of moon) , 5, 6, 119, 120, 153, 167, 174 Eclipse (of sun) , 4–6, 10, 11, 32, 34, 37, 38, H 101, 107, 119, 120, 153, 174, 196 Hale, G.E. , 107 Energy rejection fi lter (ERF) , 109, 116, 117, H-alpha. See Hydrogen-alpha 119, 124 H-alpha fi lters , 22, 93, 105–110, 113–126, Equatorial mounting , 20, 25, 26, 68–70, 80, 128, 130, 131, 133, 135, 137, 169, 120, 145, 179 181, 183 ERF. See Energy rejection fi lter (ERF) Hedgerow prominences , 126 Eruptive prominences , 126 Herschel wedge , 36, 37, 44, 125, 144, 145, Etalon , 108, 109, 111–119, 122, 124 168, 179 Exposure (in solar photography) , 24, 135, 137, Hodgson, R. , 61, 62 141, 145, 146, 150, 159, 163 Hydrogen-alpha (H-alpha) , 5, 60, 80, 93, 102, Eye, danger to from Sun , 17, 18 135, 174 Eyepiece projection , 148, 150, 156–160, 168, 173, 180 Eyepieces (for solar projection) , 30, 31, 89 I Image processing software , 174, 177, 186, 187 Imaging Source (webcam-type cameras) , F 177, 178 Faculae, polar. See Polar faculae Interference fi lters , 47, 102, 107–110, 168, 180 Filaments , 50, 51, 104, 105, 107, 111, 115, 118, 119, 125–131, 169, 170 Film, photographic , 32, 63, 138 J Filters Janssen, P. , 107 Baader (white light) , 34, 125 Ca-K , 106, 124, 125 eyepiece (DANGER!) , 18, 22, 31, 36 L

glass , 25, 34, 35, 37, 60, 98, 145, 147 L 0 , 74, 76–78 H-alpha (see H-alpha ﬁ lters) Light bridge , 54, 62, 88, 93, 98 Mylar , 32–35, 39, 59, 98, 122, 145, 168, 193 Limb darkening , 48–49, 53, 59, 140, 159, 191 Index 213

Little Ice Age , 13 Prominences , 10, 11, 22, 93, 102–105, 107, Lockyer, N. , 107 108, 110, 111, 115, 117, 119–121, Lumenera (webcam-type cameras) , 177, 178 125–131, 135, 168, 169, 171, 172, Lunt fi lters , 116, 122 180, 181, 183–186, 194–196 Lyot, B. , 107 Q M Quiescent prominences , 125–127, 130 Maksutov telescope , 24, 25, 27, 31, 35, 68, 69, 84, 144, 153, 154 R Maunder, E.W. , 13, 78 R . See Relative Sunspot Number Maunder minimum , 13 Radiative zone , 3 McIntosh sunspot classi fi cation system , 57 Re fl ector (telescope) , 19, 22–25, 27, 31, 37, MDF. See Mean Daily Frequency 68, 84, 151, 153, 180 Mean Daily Frequency , 84–86 Refractor (telescope) , 8, 19–31, 33, 37, 44, 46, Memory cards , 139, 160, 173 47, 50, 61, 68–70, 84, 87, 97, 103, Motor drives (for telescopes) , 28, 67, 135, 109, 112, 114, 115, 119, 120, 166, 167 123–125, 135, 144, 145, 147, Mylar fi lters , 32–35, 193 153–159, 162, 165–171, 175, 176, 178–180, 183, 188–190, 194 Relative Sunspot Number , 83, 86–96, 103 N Report forms , 91, 92, 94 Naked-eye sunspots , 37, 98–99 Rotation number , 70, 74 Newtonian telescope , 23, 157 NexImage (webcam by Celestron) , 176, 177, 180, 182, 183 S Satellites, effects of solar activity on , 9, 11, 13, 15 O Scanning images , 70 Off-axis mask , 23–24 Schmidt-Cassegrain telescope , 24, 27, 31, 68, Orientation of sun’s image , 26, 69, 70, 72, 69, 84, 117, 144 129, 191 SCT. See Schmidt-Cassegrain telescope Seeing , 5, 14, 42–44, 48, 50, 61, 62, 70, 80, 87–89, 93, 97–99, 106, 120, 122, P 136, 138, 145, 146, 159, 160, P . See Position angle 173–175, 179, 180, 182–184, 190 Passband , 108–119, 124, 125, 168 Self-timer , 141, 164 Penumbra , 50–57, 62, 68, 86, 88, 89, 160 Sharpening digital images , 192–193 Penumbral fi laments , 50, 51 Slow motions (on telescope mount) , 20, 26, Photosphere , 4–7, 11, 48–51, 53, 54, 59, 62, 47, 67, 68, 115, 145, 166 88, 101, 102, 169, 170, 191, 192 Solar and Heliospheric Observatory (SOHO) , Plages , 104–106, 115, 118, 119, 131 9, 11, 12 Polar faculae , 59–61, 78, 97, 98 Solar cycle , 8, 9, 11, 14, 16, 50, 58, 78, 79, 84, Pores , 53, 54, 56, 78, 86, 88, 89, 183 90, 94, 96, 97, 102, 131 Position angle , 72–76, 90, 97 Solar Dynamics Observatory (SDO) , 9 Pre- fi lter. See Energy rejection fi lter Solar fi nderscopes , 45, 46 Prime focus , 30, 122, 123, 150–155, 160, Solarscope fi lters , 109, 113, 114, 116, 122, 123 168, 180 Solar telescope , 34, 106, 108, 110–112, 115 Projection box(es) , 20, 28–31, 44, 45, 47, 60, Solar wind , 6, 11–13, 15 61, 64–67, 70, 86, 97 Spectroheliograph , 107 Projection grid , 64–67, 90, 97 Spectrohelioscope , 107, 108 Projection method , 23, 30, 31, 45, 61, 64–80, Spectroscope , 107 89, 98, 128, 150, 190 Spicules , 127, 181 214 Index

Spörer, G. , 78 Tele-extender , 158 Spörer’s law , 78, 90 Transition region , 6, 9 Stars (compared with sun) , 1–3, 6, 17, Transition Region and Corona 22, 120, 171 Explorer(TRACE) spacecraft , 9 STEREO spacecraft mission , 16, 55 T-ring , 120, 154, 156–158, 164 Stonyhurst discs , 71, 72, 74, 76, 77, 86, 90 Sun diagonal. See Herschel wedge Sunspot cycle , 7–9, 13, 70, 71, 78, 79, 96, U 97, 125 Umbra , 50–56, 77, 86, 88, 93, 99 Sunspot groups , 7, 9–11, 15, 37, 47–51, Unsharp mask , 189, 193 53–62, 75, 76, 78–80, 83–87, 89, 93, 96, 98, 99, 104, 105, 118, 126–128, 130–135, 145, 146, 148, W 156, 158, 159, 166, 174, 186 Weather, sun’s effect on , 1, 12, 13, bipolar , 51, 53, 55–57, 75 15, 43, 44 Sunspots Welder’s glass , 37, 99 classi fi cation , 55–59 White-light fl ares , 61, 62, 80, 93, longevity , 54 97–98, 131 magnetic fi elds , 59 Wilson, A. , 52 numbers , 53, 55, 59 Wilson Effect , 52, 53 positions , 63, 64, 67, 71–74 Wolf, J.R. , 87 temperature , 7, 13 Wolf Number. See Relative Sunspot Number

T T-adapter , 154 Z Teleconverter , 152, 154–156, 159, 160, 167, Zurich Number. See Relative Sunspot 169, 188, 189 Number