Project Manual Fall 2011

Astronomy 111 Project Manual Fall 2011

Revolution of the moons of Uranus, Neptune and Jupiter, Kepler’s third law, and Newton’s law of gravity

1 Introduction

This is an observing experiment in which we will determine the mass of three of the Solar system’s giant lanets, by measuring the orbital properties of their moons and analyzing their motions. Along the way we will use Jupiter and its moons, specifically, to validate Newton’s law of gravity and Kepler’s third law.

This observing project will involve visits to the telescope frequently over the course of 3-4 weeks, including at least one sequence of four consecutive nights and five nights in a week. Everybody in the class will go to the telescope – in groups of three or four at a time – with the object of sharing all of the data. Each student will perform his or her own analysis and write an independent report on the results.

During the first week in October, we will derive Kepler’s third law,

2 2 4π 3 P= (aa12+ ) , (1) Gm( 12+ m) from Newton’s laws of motion and law of gravity. Here P is the period of revolution of two bodies about each other, m1 and m2 are their masses, a1 and a2 are the semimajor axes of their elliptical orbits, measured from the center of mass of the two-body system, and mm1 2= aa 21. If one of the masses, say, m1 , is much larger than the other, then the more massive member can be taken to be fixed (because its semimajor axis is small), and the smaller one can be considered to do all the orbiting, with Kepler’s third law simplifying to

4π 2 Pa23= . (2) GM

This approximation applies, of course, to the period and orbital semimajor axis of each planet in the solar system, taking M to be the mass of the sun. It also applies to the moons of Uranus, Neptune and Jupiter, in orbit around the much-heavier planet. In one of the first notable uses of a telescope, Galileo showed that Jupiter and its satellites look like a miniature solar system, and thus provided substantial evidence that Copernicus’ heliocentric model of the solar system was viable.

In this experiment, we will monitor the motions of the satellites of Uranus, Neptune and Jupiter. From the data gathered, we will be able to measure the orbital period and semimajor axis of each of these satellites. The experiments consist of a series of observations with a CCD camera on the Mees 24-inch telescope; we will take images in which we can identify the moons and determine the distance between each moon and its host planet as a function of time.

The moons of the giant planets all travel in orbits that are very nearly circular. The orbits are also very nearly coplanar; the moons appear to be lined up because we are looking almost edge-on to this plane. We can only see the projection of each moon’s orbital radius in the plane perpendicular to the line of sight between the Earth and each planet, as in Figure 1. This apparent distance is Raapparent = sinϕ , where a is the distance from the moon to the center of its host planet, and ϕ is the “azimuthal” angle of the moon’s

radius with respect to the line of sight toward the planet. For each moon, the determination of the maximum value of Rapparent comprises the measurement of its orbital semimajor axis, and determination of the time between successive maxima comprises the measurement of its orbital period. But ϕ increases proportionally with time; therefore plotting Rapparent as a function of time will yield a sine curve, of amplitude a and period P, the period of the moon’s orbit. Once we know a and P in any units, we can validate Kepler’s third law, Equation 2.

Note that this works even if there are time gaps in the data – as one usually gets between sunrise and sunset, or due to cloudy nights – as long as one can fit a sine function to the data.

2 Procedure

2.1 At the telescope

Figure 1: geometry of observations. (From the CLEA lab You will be instructed personally by the manual) instructors in the startup and shutdown procedures for the telescope and CCD camera, in the course of which you will become familiar with the checklists we maintain for these tasks. You will also learn how to use TheSky, a planetarium program that we use to control the telescope at Mees, and CCDSoft, which controls the camera. Since this will be the first time observing for most of you, though, the initial telescope, camera and computer setup will be done for you. Here we will discuss just the observing procedures you’ll follow after everything is powered up and running.

Note, throughout, that by “take an Figure 2: apparent orbital radius vs. time. (From the CLEA lab image” is meant: tell CCDSoft to take the manual). image, save this image as a file with a name that helps you remember what it is (e.g. “Neptune_V_60sec.fits”), and record

in your observing notes a description of the image, and the UT date and time on which it was taken (e.g. “Neptune_V_60sec.fits: Neptune and Triton in the V filter, 60 sec, optimized for Triton, 1 September 2011, 00:45 UT”).

1. Begin by pointing the telescope at Neptune, which is the earliest riser of our three planetary targets, these days. Start by moving the diagonal mirror on the bottom of the telescope to the position that permits the eyepiece to see. Then use TheSky to move the telescope to Neptune. (One of your team should go upstairs at this point, and move the dome so that the telescope can look out the slit.) Bring the planet into the center of the field, using the telescope paddle, and adjust the focus (also on the paddle) to produce a sharp image. You will see Neptune and its brightest moon, Triton. Make sure everybody gets a chance to view Neptune and Triton through the main telescope and eyepiece.

Next, return the diagonal mirror to the CCD camera’s view, and restore the Focus setting to the value last used for taking images. Take an image of Neptune with the CCD camera, using CCDSoft. By moving the telescope slightly with the guiding paddle between short exposures with the camera, make careful note of the correspondence among the directions on the CCD display (up, down, left, right) and the directions on the sky and buttons on the paddle (NSEW). Center Neptune in the CCD’s field. In doing so you will find it helpful to note that at Mees the dimensions of the ST-9 CCD’s field of view on the sky are 4.2 arcminutes square.

2. Check the focus of the telescope, using Triton and Neptune. First, set the exposure time such that the moon is easily seen. Then, using the paddle, run the telescope focus out until the images of the moons look significantly blurred. Then run it in in small increments (5-20) of the focus position reading (on the telescope status monitor), recording the diameter of the stellar image and the peak signal at every step; observe the diameter decrease to a minimum and then increase again. If at any point the peak signal is more than about half the CCD’s maximum signal, reduce the integration time, and go back to the beginning of the focus-adjustment sequence. Note the focus readout value corresponding to the minimum diameter images. Then run the focus out again, well past the minimum-image size point, and run it back in slowly until you reach the correct focus readout value. Center Neptune in the CCD’s field again. Save an image of this scene, at the exposure time you used for focusing and at a shorter time to make a nice picture of Neptune itself. The instructors may want to re-initialize the telescope position at this point; tell one of them when you reach it.

3. When this focus adjustment is complete, take note of the peak signals and the diameter of the half-peak-signal level in the images of the moons (given at the bottom of the CCD’s image window as “I”), and write the value of the diameter, in arcseconds, in the control room’s Observing notebook. Note that the plate scale is about 0.5 arcsec per CCD pixel, at Mees. The diameter of a moon’s image should be no larger than a couple of arcseconds. Neptune, on the other hand, is about 2.3 arcsec in diameter this month, so its apparent diameter will bear substantial contributions from both its real size and the blurring by the atmosphere. If the system is well focussed, the apparent angular diameter of the much smaller Triton is dominated by blurring from turbulent variations of the refractive index of the atmosphere, an effect often referred to as seeing. (That is, Triton is smaller than the image-blur from the atmosphere, and Neptune is similar in size to this blur.)

On the basis of your experience in the focusing, choose two integration times: one such that the peak signal of Neptune stays well below the maximum range of the CCD, and one that brings out Triton well enough to see its location, without overexposing Neptune to the point that it no longer looks round. (One still can find the center of the planet, if the overexposed image is still round.) Take one image of the Neptune-Triton system with each integration time. Keep track of

all integration times used, and plan to take dark frames for each integration time.

This may be a good point at which to take a nice color image of Neptune. Check the time, and ask the instructors for help in using the color-imaging feature of the ST-9 CCD camera. Make sure you also have images of an A-type star like Vega, but preferably closer in magnitude to Neptune (about 6th; Vega is zero magnitude, and A0 stars like Vega have the same magnitude at all wavelengths). Something like the first of the exposure times determined above would probably be right for the individual frames of the color image.

4. If Uranus is high enough in the sky to permit observation, point the telescope at it, and repeat the procedure of step 3. Choose at least two exposure times, one of which shows the moons well but which may overexpose the planet, and one which shows the planet well. Identify the moons in your image: you should see at least four, which in order of brightness are Titania, Oberon, Ariel and Umbriel. With more effort, good conditions and luck you might also see the much fainter Miranda.

Again, take at least two images of the Uranian system: one that brings out the positions of the moons without excessive overexposure of the planet. Keep track of the integration times used, and plan to take dark frames for each integration time.

Again, this may be a good point to take a nice color image of Uranus. Again make sure you also have images of an A-type star like Vega, but preferably closer in magnitude to Uranus (about 6th).

5. As soon as Jupiter rises into view, it’s time to point the telescope at it. Take a few images of the Jovian neighborhood to make sure you can identify where each of the four Galilean moons is. (Note that it is possible for them to hide behind or in front of Jupiter, albeit briefly.) The instructors will help you determine which moon is which; this can be determined by how far away from Jupiter each is, how fast each appears to be moving, and what color each of them appears to be. At Mees you will always be able to get Jupiter, Io and Europa in the same frame, but you may need to move the telescope to get Ganymede and Callisto in the same frame as one of the others. After this, move the telescope so that Jupiter and as many of the moons as possible are distributed nicely across the CCD.

Now take several images of the Jovian system: some that bring out the positions of the moons without excessive overexposure of the planet, and one that shows Jupiter nicely. If Callisto and/or Ganymede are too far away to fit in the same frame as Jupiter, then “bootstrap” your way to them by constructing a small series of overlapping images with other moons and maybe stars providing the reference back to Jupiter. Again, keep track of the integration times used, and plan to take dark frames for each integration time.

Yet again, this may be a good point to take a nice color image of Jupiter. Again make sure you also have images of an A-type star like Vega for comparison. In this case Vega will do, as Jupiter is even brighter than Vega. With suitably longer exposures you could do the same for the Jovian moons, which is also interesting, as Europa turns out to be quite white, and Io distinctly red.

6. Repeat this sequence – steps 3-5 – about once per hour for the rest of the night, or until the planets set. Take images more frequently frequently for the moons that are moving rapidly across the sky, which they will when they get close to their planets. Make sure you continue to note in your lab book the conditions (integration time, object, filter etc.) under which each image was taken, and which of the targets is in each image.

7. Stargazing. Repeating the planet sequence every hour will leave ample time for making images of other interesting targets. Everyone in the group should also choose a non-planetary celestial object of which to take a nice image, hopefully in color, with the CCD camera. Suggestions are given below (section 4). We will post all the pictures on the AST 111 Web site.

8. When you have completed your work, close the camera shutter, take and save a dark frame for each integration time you used, again both in FITS and JPEG formats. Copy all of your data files to a flashdrive or CD. When you return to campus the instructors will help you zip them together and upload them to the AST 111 Wiki.

9. For inclusion in your lab report, you should note the conditions of observing; the weather, the operation of the telescope, and the observing procedure. Include telescope pointing and focus- position information. Describe the objects you observed and what you saw.

2.2 Data reduction

The main results we are after are the distances between the center of each planet and the center of each moon, in units of the planet’s radius as a function of time. Neptune’s diameter is affected significantly by seeing, and the orbit of Triton is not viewed as close to edge-on as the other moons these days. To simplify this matter we will simply record from the images in CCDSoft how many pixels east and north of the center of the planet Triton is.

For each image you have recorded the time, now all you have to do is measure the distances. There are several ways you can do this.

2.2.1 Low-tech

1. Print paper copies of all the images you will use. Work one night at a time; don’t mix data from different nights. Distribute the images among your lab team, and set each person to work.

2. From good (i.e. not overexposed) images of the planet: measure with a ruler the equatorial diameter, and calculate its radius. (Note, by the way, that the polar diameter of Jupiter is measurably smaller than the equatorial diameter.)

3. Then, on each other image with a planet and its moons, locate as precisely as possible the center of Jupiter and measure the distances between Jupiter’s center and that of each moon. Divide the distances you measure by that you measured for Jupiter’s radius. These final numbers are the apparent positions of the moons; plotted as a function of time they should each vary sinusoidally, as in Figure 2.

4. In the cases of Jupiter and Uranus the orbital planes are seen close enough to edge-on that the moons will appear to move back and forth along a line, and only one dimension of distance is necessary. In the case of Neptune and Triton the orbital plane is more steeply inclined, so we will have to measure distances parallel to and perpendicular to the apparent major axis of the orbit. This in turn will be more easily determined after we have all of the semester’s Neptune images in hand.

2.2.2 Not quite as low-tech

1. Import all of your JPEG files, one per page and at the same scale, into any Microsoft Office application, such as PowerPoint or Word. Distribute these pages among your team, and put all members to work.

2. In the Drawing tools menu, select Arrange…Align…Grid Settings, check the “Snap objects to other objects” box, and uncheck “Snap objects to grid.”

3. Using the drawing tools, draw ellipses on top of these images that fit each of the images of the planet.

4. For each image, draw one vertical line and one horizontal line, and drag them over the planet’s ellipse until they snap onto the center guides, and intersect at the ellipse’s center.

5. Draw a line from each moon to the intersection of the two lines, noting that the end of your new line will snap onto the intersection.

6. Right-click on each new line, and on the planet ellipse, choose “Size and position…”and read off the lengths and radii of the objects. Note that for lines this gives the projections along the horizontal and vertical directions rather than the length directly, so use the Pythagorean theorem to get the length. Divide the distances you measure by that you measured for the planet’s radius. These final numbers are the apparent positions east or west of the planet, of the moons; plotted as a function of time – and taking one of the directions, conventionally west, to be negative – they should each vary sinusoidally, as in Figure 2.

See Figure 3 for an illustration of this process.

Figure 3: illustration of the process described in section 2.2.2, using PowerPoint to draw objects and measure lengths. The image is of Europa, Jupiter and Io, taken at Mees Observatory with an SBIG ST-9 CCD camera and a V (wavelength 550 nm) filter. Jupiter is slightly overexposed, to permit the moons to be located accurately. On top of this image is drawn an ellipse the same size as Jupiter (orange), two perpendicular guides snapped to intersect at Jupiter’s center (blue), and lines with one end snapped to the intersection, and the other end centered on a moon. Io is west of Jupiter in this image, so

the position of Europa would be plotted as +7.28 Jupiter radii, and that of Io as -4.66 Jupiter radii.

2.2.3 Either way

Prepare a table of UT and apparent position of each moon at that UT, as a summary of your results. Estimate the uncertainty in each of your measurements, and include those estimates in your table as well. Note that you will need to record whether the moon is located east or west of the planet, as well its apparent distance in planet-radius units. Post your results on the AST 111 Wiki,

Also post any nice-looking images to the Wiki, and/or email them to to Dan ([email protected]), together with a description of your observation (object, wavelength, exposure time, names of team members), for inclusion in our class’s Online Observing Gallery in the AST 111 Web site.

3 Data analysis

3.1 Orbital radii and periods for the satellites

1. Once all the observations are done for the season, collect all of the data from the AST 111 Wiki and make a table of UT (including Julian day as well as time) and apparent position (in Jupiter radii) for each moon. For convenience in plotting, express the JD-UT combination in decimal form in units of days. For example: as I type these words it is 24 September 2008, 4:42 PM EDT. The JD for the date is 2454734, and the UT for this time (four hours later than EDT) is 9:42 PM = 21:42 = 0.90 days, so I would plot this date and time as 2454734.90.

2. Then, for each moon, plot apparent position as a function of time. From each plot, determine the amplitude (maximum apparent position) in planetary radii and period (time between consecutive maxima) in days. Again there are multiple acceptable ways to do this.

3.1.1 Low-tech

1. Sketch a smooth, sinusoidal curve by hand through the data points, noting the size of the uncertainties. This of course will work best if there are lots and lots of data samples uniformly spread over each orbital period.

2. Read off the amplitude and the period from your graph for each planet. This gives directly the orbital radius in planetary radii, and the orbital period in days, for each moon. The uncertainty in the final result would be somewhat higher with this method than it would be for one that’s…

3.1.2 Not quite as low-tech

1. On the Projects page on the AST 111 website, you can find an Excel workbook called jupiter.xls, which is designed to help you fit since curves through the data. Download this file, and save a copy of it for each moon-planet combination.

2. Then put the data – UT in days and apparent position in planetary radii, in columns, in that order – into the columns on the first sheet of this workbook. On the third sheet you will see these results plotted. On the second you will find places to enter three choices for amplitude, period, phase difference (offset of the first planet-crossing from the zero of time, in days) and vertical offset (which should be very close to zero), that will result in three different-color sine curves being drawn on top of your data.

3. Adjust the amplitude, period, phase difference and vertical offset until you get a curve that is a good fit to your data, and save that version of each workbook; the resulting amplitude and period are the orbital radius in planetary radii, and the orbital period in days, for that particular moon.

3.1.3 Either way

Tabulate your results: name, orbital radius a (in planet radii) orbital period P (in decimal days) for each moon, and an estimate for the uncertainties in these quantities.

3.2 Kepler’s third law, Newton’s law of gravity, and the masses of the giant planets

1. From your table, calculate a3 and P2 for each of the Jovian satellites, and plot a3 as a function of P2 . Label the axes appropriately. What is the shape of the curve that results? Does the precise distance to the Jovian system matter – that is, do the values of the as in centimeters, instead of Jupiter radii, matter?

2. Repeat for the Uranian system, in a separate plot.

3. In a paragraph or two, discuss these results in the light of Kepler’s third law (Equation 2).

4. Kepler’s laws are consequences of Newton’s law of gravity. In a paragraph or two, discuss the degree to which your results support Newton’s law of gravity.

5. Of course we do know how far away the planets are, and can measure their radii from their angular radii: the results are r = 2.476,2.556, and 7.149× 109 cm (Neptune, Uranus and Jupiter). Using this value and Equation 6.2, convert each a into centimeters, each P into seconds, and deduce the mass M of each planet in grams. Use average and the spread of the four values you have that result to arrive at a “best” value and an estimate of the uncertainty in your determination of Uranus’s and Jupiter’s masses.

4 Stargazing

With a good modern CCD camera and a 24” telescope that tracks fairly well, such as those you’re using at Mees, one can take high-quality images of astronomical objects in a remarkably short time: in a few minutes one can have images that astronomers used to spend hours on much larger telescopes to acquire in the days of photographic plates. Thus it would be god for you to take advantage of a visit to Mees, and see what it’s like to take pictures of interesting, relatively faint astronomical objects. Here are some suggestions.

1. Multiple stars. This can help determine accurately the plate scale and orientation of your images. In Table 1 a list of multiple stars is given, along with their separation in arcsec and the position angle (measured east of north) from primary (brighter member of the system) to the others. The perennial favorites, Mizar/Alcor in the handle of the Big Dipper, and Albireo in Cygnus, will be conveniently observed for large portions of the night.

2. Star clusters. Of the two kinds of star clusters in the sky, the rounder, more compact sort – called globular clusters – look nicer in telescopes. A list of bright globular clusters appears in Table 2. (The other kind, called open clusters, look better in binoculars or even with the naked eye. Try the Hyades and the Pleiades, conspicuous open clusters in Taurus, with our image-stabilized binoculars on the telescope catwalk while the telescope is busy.)

3. Nebulae. There are three kinds of visible nebulae: H II regions, large and usually irregular ionized clouds associated with very young massive stars; supernova remnants, the remains of the explosions that terminated the lives of very massive stars; and planetary nebulae, the relatively small, symmetrical clouds of rings of ionized gas surrounding dying low-mass stars, that of course have nothing whatsoever to do with planets. (To understand the origin of the name, which was coined in the early nineteenth century, observe the Saturn Nebula, NGC 7009.) Fall isn’t a very good time to observe H II regions, because they all lie along the plane of the Milky Way. Thus we suggest that you concentrate on planetary nebulae, a list of which is given in Table 3. If you must observe a supernova remnant, try the Crab Nebula, M1, the remnant of the supernova of 1054 AD; it is reasonably bright and fits very nicely in the CCD camera. It’s on the high-RA side of Taurus, and so will be viewed best just before it starts to get light in the morning.

4. Galaxies. Face-on spiral galaxies are the prettiest, but the most famous examples that are up in the Fall (e.g. M31 and M33) are too big to fit in most telescope focal planes; these are best observed by eye with the 6” guider telescope, on the side of the main telescope at Mees, or with binoculars. Most of the face-on spirals that fit in the CCD camera’s field are fairly faint and may involve several-minute exposures with the CCD camera. The brightest relatively compact spirals that are up in the Fall are M77 and M74. M74, a normal spiral galaxy seen very close to face-on, is a particularly good fit to the CCD camera’s field of view. M77 is highly recommended, because it is the best and brightest example of a Seyfert galaxy. The main reason that Seyfert galaxies are interesting is that they can be shown to contain supermassive black holes, surrounded by accretion disks, at their centers. Other possibilities are listed in Table 4.

The objects in the following tables have been selected for being up at night during the Fall, for brightness, and usually for relatively small angular size (befitting the use of CCD cameras or eyepiece observing depending upon the eyepiece used).

Table 1: Bright multiple stars

Star RA, DEC P.A. θ Sep. Primary V Secondary V Common (2000) (degrees) (arcsec) name ζ Psc AB 1 13.7 +7 35 62 22.7 5.2 6.2 γ Ari AB 1 53.5 +19 18 357 7.5 3.9 3.9 α Psc AB 2 02.0 +2 46 269 1.8 4.3 5.2 γ And A-BC 2 03.9 +42 20 63 9.6 2.1 4.8 Almach α CMa AB 6 45.1 -16 43 111 6.3 -1.5 8.5 Sirius* α CMi AB 7 39.3 +5 14 102 3.5 0.4 10.8 Procyon* ι Cnc 8 46.7 +28 46 307 30.7 4.0 6.6 γ Leo AB 10 20.0 +19 50 125 4.4 2.6 3.8 ξ UMa AB 11 18.2 +31 32 252 1.8 4.3 4.8 Mizar/Alcor ζ UMa AB 13 23.9 +54 56 152 14.6 2.2 3.9 κ Her AB 16 08.1 +17 03 12 27.3 5.1 6.2 α Her AB 17 46.6 +14 23 104 4.6 3.5 5.4 Rasalgethi β Cyg AaB 19 30.7 +27 58 54 33.7 3.1 5.1 Albereo δ Cep AC 22 29.2 +58 25 191 42.1 4.1 6.3 * The companion stars in these cases are white dwarfs, the observations of which are extremely challenging owing to their faintness relative to the bright primary stars.

Table 2: globular clusters

Common Other name RA (2000) Dec (2000) V Comments, name (mag)  Dan’s favorites NGC 5024 M 53 13 12 55.3 18 10 09 7.6 NGC 5272 M 3 13 42 11.2 28 22 32 6.2  NGC 5904 M 5 15 18 33.8 02 04 58 5.7  NGC 6171 M 107 16 32 31.9 -13 03 13 7.9 NGC 6205 M 13 16 41 41.5 36 27 37 5.8  Great Hercules Cluster NGC 6218 M 12 16 47 14.5 -01 56 52 6.7 NGC 6254 M 10 16 57 08.9 -04 05 58 6.6 NGC 6341 M 92 17 17 07.3 43 08 11 6.4  NGC 6333 M 9 17 19 11.8 -18 30 59 7.7 NGC 6356 17 23 35.0 -17 48 47 8.3 NGC 6402 M 14 17 37 36.1 -03 14 45 7.6 NGC 6712 18 53 04.3 -08 42 22 8.1 NGC 6760 19 11 12.1 01 01 50 8.9 NGC 6779 M 56 19 16 35.5 30 11 05 8.3 NGC 6838 M 71 19 53 46.1 18 46 42 8.2 NGC 6934 20 34 11.6 07 24 15 8.8 NGC 7078 M 15 21 29 58.3 12 10 01 6.2  NGC 7089 M 2 21 33 29.3 00 49 23 6.5

Table 3: planetary nebulae Name Other RA (2000) Dec (2000) Largest V Comments, (NGC) name dim (mag)  Dan’s favorites (arcmin) 40 00 13.0 72 32 0.6 11 246 00 47.0 -11 53 3.8 8 650/651 M76 01 42.3 51 34 4.8 12 Butterfly Nebula IC 289 03 10.3 61 19 0.6 12 1514 04 09.2 30 47 1.9 10 1535 04 14.2 -12 44 0.7 10 IC 418 05 27.5 -12 42 0.2 11 IC 2149 05 56.3 46 07 0.1 11 2392 07 29.2 20 55 0.7 10 2438 07 41.8 -14 44 1.1 10 2440 07 41.9 -18 13 0.5 11 3242 10 24.8 -18 38 20.8 9 3587 M97 11 14.8 55 01 3.2 11 Owl Nebula 4361 12 24.5 -18 48 1.8 10 IC 3568 12 32.9 82 33 0.1 12 IC 4593 16 11.7 12 04 2.0 11 6210 16 44.5 23 49 0.2 9 6309 17 14.1 -12 55 1.1 11 6543 17 58.6 66 38 5.8 9  Cat's-eye Nebula 6572 18 12.1 06 51 0.1 9 6720 M57 18 53.6 33 02 2.5 9  Ring Nebula 6741 19 02.6 00 27 0.1 11 6790 19 23.2 01 31 0.1 10 6803 19 31.3 10 03 0.1 11 6818 19 44.0 -14 09 0.3 10 6826 19 44.8 50 31 2.3 10 6853 M27 19 59.6 22 43 15.2 8 Dumbbell Nebula 7009 21 04.2 -11 22 1.7 8  Saturn Nebula 7027 21 07.1 42 14 0.3 10 7048 21 14.2 46 16 1.0 11 7662 23 25.9 42 33 2.2 9

Table 4: galaxies Name Other RA (2000) Dec (2000) Largest V Comments, (NGC) name dim. (mag)  Dan’s favorites (arcmin) 7814 00 03.3 16 09 6.3 10 … IC 10 00 20.4 59 18 5.1 10 147 00 33.2 48 30 12.9 9 157 00 34.8 -08 24 4.3 10 185 00 39.0 48 20 11.5 9 205 M110 00 40.4 41 41 17.4 8 Companion of Andromeda Nebula 210 00 40.6 -13 52 5.4 10 224 M31 00 42.7 41 16 178.0 3 Andromeda Nebula

Name Other RA (2000) Dec (2000) Largest V Comments, (NGC) name dim. (mag)  Dan’s favorites (arcmin) 221 M32 00 42.7 40 52 7.6 8 Companion of Andromeda Nebula 247 00 47.1 -20 46 20.0 8 278 00 52.1 47 33 2.2 10 … IC 1613 01 04.8 02 07 12.0 9 404 01 09.4 35 43 4.4 10 488 01 21.8 05 15 5.2 10 524 01 24.8 09 32 3.2 10 584 01 31.3 -06 52 3.8 10 596 01 32.9 -07 02 3.5 10 598 M33 01 33.9 30 39 62.0 5 Triangulum Galaxy 628 M74 01 36.7 15 47 10.2 9  Nice face-on spiral 660 01 43.0 13 38 9.1 10 672 01 47.9 27 26 6.6 10 720 01 53.0 -13 44 4.4 10 772 01 59.3 19 01 7.1 10 821 02 08.4 11 00 3.5 10 891 02 22.6 42 21 13.5 10  Nice edge-on spiral 925 02 27.3 33 35 9.8 10 936 02 27.6 -01 09 5.2 10 1023 02 40.4 39 04 8.7 9 1042 02 40.4 -08 26 4.7 10 1052 02 41.1 -08 15 2.9 10 1055 02 41.8 00 26 7.6 10 1068 M77 02 42.7 00 01 6.9 8  Brightest Seyfert galaxy 1084 02 46.0 -07 35 2.9 10 1232 03 09.8 -20 35 7.8 9 1300 03 19.7 -19 25 6.5 10 1407 03 40.2 -18 35 2.5 9 … IC 342 03 46.8 68 06 17.8 9 1637 04 41.5 -02 51 3.3 10 2336 07 27.1 80 11 6.9 10 2655 08 55.6 78 13 5.1 10 2985 09 50.4 72 17 4.3 10 3147 10 16.9 73 24 4.0 10 6503 17 49.4 70 09 6.2 10 7217 22 07.9 31 22 3.7 10 7331 22 37.1 34 25 10.7 9 7457 23 01.0 30 09 4.4 10 7606 23 19.1 -08 29 5.8 10 7640 23 22.1 40 51 10.7 10 7727 23 39.9 -12 18 4.2 10