Galaxies in Leo and Virgo

There are many fine galaxies available for study within the constellations of Leo and Virgo. Many of the galaxies can be observed with smaller telescopes (a good dark sky location will help considerably). There are a Bakers' Dozen of galaxies in this group. They can be seen with 8" or larger telescopes from Fox River Valley area Road and with smaller telescopes from the area near Elburn, Illinois. Most of them are rated as visual index 4 objects, with a few of them being visual index 5. Visual index 5 is about the limit of what one can see in suburban skies, although the local lighting and the sky transparency can make a large difference in the visibility of any of these objects. For comparison purposes, M1 is visual index 3.

Most of them are best seen at fairly low powers, under 100 being fine. Many experts recommend a 45 arc-minute field of view, which corresponds to a power of about 75 with a 55 degree apparent field of view eyepiece. So, for example, with an 8 inch f/10 scope, you should probably use an eyepiece with a focal length of about 25mm. It may be advantageous to use a wide-band light pollution filter. The narrow band filters are usually better for planetary nebula, since they are often 'tuned' to transmit only very specific, narrow, wavelengths of light. Galaxies usually emit light over a much broader spectrum, so the wider band filters are usually best. Mark Christensen has seen these galaxies from his home north of St. Charles with his 8" f/5.5 Newtonian, sometimes without using a filter.

Constellations: Leo & Virgo Constellation Leo As shown in figure 1, one of the best places to start when searching for galaxies within Leo is with M66 and M65. Look for the distinctive triangle formed by Denebola (Mag 2.12), Zosma (Mag 2.53), and Chertan (Mag 3.31) – due to their magnitudes, they are easy to see! Then look just to the southeast of Chertan to find M66 and M65, about 2.5 degrees away. If your finder has a four degree field of view, then M65 and M66 will be located just off the lower left edge of the finder. Move the telescope east and slightly south until Chertan is near the far edge of the finder. At this point, M65 and M66 should be very near the center of your finder. Move the telescope another .5 degree southeast to center the objects. They have an angular separation of only 19 minutes and are quite small (about 5 minutes on a side).

Figure 11

About 7 degrees southwest of Chertan (Leo) is 52 Leonis. This star makes an excellent path to M105, M96, and M95. Center 52 Leonis in the finder and then move the telescope 1.5 degrees to the south (approximately one-half way across the finder in a four degree finder). You should now be centered upon M105. M105 is a tightly packed globular looking galaxy of 11th magnitude and very small size. Another one degree south of M105 lies M95. M95 is magnitude 10.5, oval in shape and approximately five minutes by five minutes in size. Moving west one degree brings you to M95. It is a small spiral galaxy of magnitude 11. M66, also known as NGC3627 (shown in figure 2) is a magnitude 10 object.

 

Figure 21

M65, also known as NGC3623, is a magnitude 10.5 object and appears as shown in figure 3.

Figure 31

A group of thirteen galaxies lie at the eastern end of Leo, between the two arms of Virgo. For purposes of 'star-hopping', we'll break them into two sub-groups, one of three galaxies which we will find starting at Denebola (the tail of the triangle in Leo), and the other ten we will find starting from Vindemiatrix (Virgo), the northernmost star in the upper arm of Virgo.

The First Three

From Denebola we will find M98, M99, and M100. I'll assume the width of your eyepieces field of view is 45 arc-minutes (remember, this corresponds roughly to a 25mm Plossl eyepiece working with a 80 inch focal length) and that your finder has a four degree wide field of view. Start by centering your finder on Denebola and make sure it is centered in your scope. Now, to find M99 (the brightest of the three), move the telescope 6.5 degrees east using the finder. This is easy to do with a polar mount but if you can, first orient yourself with a pair of binoculars, it will be easier to interpret what you see in your finder. In any case, if you start with Denebola centered then you will have moved 2 degrees when it just disappears from the edge of you finder field of view. Why? Because the field of view of the finder is 4 degrees (so we assumed), remember? In any case, when Denebola just disappears from the finders field of view stop. Now pick a reasonably bright star that is just coming into the opposite (from Denebola) side of the field of view. Resume sweeping to the east until that star has just disappeared from the western edge of your field of view. You now have moved 6 degrees (4 2) to the east of Denebola. Slight north and east (about 1/2 degree in each direction) of the center of your finders' field of view should be a 5th magnitude star, called 6 Coma Berenices (see figure 4). This is our jumping off point.

If you get lost, don't worry: Just sweep back to the west until Denebola is centered and try again. Worst case, center Denebola, and wait for about 30 minutes. The rotation of the earth will have brought 6 Coma Berenices to near the field of view of your eyepiece.

Figure 41

So now we know how to get to 6 Coma Berenices, our gateway to three galaxies. Center 6 in your finder and confirm that it is centered in your telescopes eyepiece. To find M99, nudge the telescope south so 6 just disappears from the edge of the field of view of the scopes' eyepiece. Now move the same distance east. M99 should be near the center of the eyepiece. Its fairly small, only 5 by 4 minutes of arc, or about 10% of the eyepieces field of view. If you have a hard time seeing it, go back to 6 Coma B and try again. If the star field looks the same each time you are probably looking right at it. Try averted vision or a light pollution filter. Depending on the sky conditions it may be hard or easy to see.

M99 is the brightest of the first three. If you can't see it there are two possibilities: Either the viewing is bad or your looking in the wrong place. To check this, go back to 6 Coma B. Make sure it is centered in your scope's field of view. Now move 1 degree to the west (back towards Denebola from 6 Coma B) to M98. If you start with 6 Coma B centered and move west so it is on the eastern edge of the field of view, 1 degree is located just inside the western edge (because the field of view is 45 minutes, so 45/2 45 = 67 minutes, or 1 degree 7 minutes). Bring the western edge to the center. You should be looking at M98. M98 is fainter than M99 and is 8 minutes by 2 minutes, so it is about the same size as M99 but a bit longer and thinner.

If you can't find M98 or M99 there is one sure way of deciding if the seeing is just plain bad. Go back to Denebola and nudge the scope north until Denebola is about half way to the edge of the field of view. Wait for 20 minutes (with the motor turned off!) and look again. M99 should be right in the center of your field of view. If you can't see it, I suggest you spend the night looking at double stars!

Finally, to find M100, go back to 6 Coma B. Now move (using your finder or the main scope), 1 degree north and 1.3 degrees east. M100 should be centered. It is visual index 5 (like M98) and at 6 minutes by 5 minutes is a little bigger than M99. If you have trouble, go back to 6, go 1 degree north and then wait about 7 minutes. M99 should be centered.

That completes our tour of the first three of the Leo/Virgo galaxies. Now onto the other ten.

Figure 51

The Ten

As we said before, we will start this excursion through the galaxies at Vindemiatrix, also known as Eta Virg. Eta is about five degrees south of Denebola and about half way (and south) from Denebola to Arcturus (the base of the kite of Bootes). Vindemiatrix is about 1 hour and 20 minutes east of Denebola and five degrees south, to put it another way. In any case, locate Vindemiatrix and center your finder and your scope on it. Get ready for a ride: We are going to work our way through nine galaxies starting from this point.

First stop is M60. To find it, go about 1 degree north of Vindematrix and sweep a little less than 4 degrees to the west. M60 should be in the center of the field but you may have M59 instead. They are only about 30 arc minutes (1/2 degree) apart. To make sure, move about field of your eyepiece (again, assuming it has a 45 arc minute field of view) to the east. M60 should be to the east in your field of view (rock the scope if you need to confirm which direction is which) and M59 to the west. M60 is nearly twice the size of M59. Both are visual index 4 objects. Midway between them and to the north in the same field of view is a fainter galaxy, NGC 4647. If you can see both of M59 and M60, try for it.

Make sure you know which galaxy you are looking at as this is the kickoff point for M58, which lies about 1 degree to the west of M59.

Center M59. Again, it is the westerly of the two galaxies. Now move north about 20 arc minutes and then about 1 degree to the west. M58 should now be centered. It is about the same brightness and size as the other two.

If you were not able to find these three galaxies starting directly from Vindemiatrix do not despair: There is another way. Go back to Vindemiatrix and, using your finder, go 4 degrees (barely the width of the finder field of view) directly to the west. A degree or so below the center of the finder should be a reasonably bright, widely-spaced, double star, whose components are less than degree apart. This is rho Virg. Center rho in your telescopes field of view and sweep 2 degrees north (so that rho is at the southern edge of the finder field of view). M59 and M60 should now be in your scopes' field of view. Once you have identified them, go 1 and degree to the west to find M58, as described above.

Three down, six to go. Admire and enjoy them. Once you find them the first time, go back and start from scratch again. Easy, huh?

Now center M58 in your scopes' field of view (as always, I'm assuming you have a 45 arc-minute field of view). See figure 6. Move it half-way to the west of your eyepiece. Now go north about 1 degree. M89 (visual index 4, 7 by 4 arc minutes in size) should be centered in your field of view. After you identify it, go another degree north to M90. M90 is fainter at visual index 5 and has a size of 10 by 5 arc minutes. Finally, go about 1 and degree north to M91, which is the same brightness but only 5 by 4 minutes in size.

Figure 6 – Galaxies seen against Telrad Finder1

Think we're done with this chain? Nope, one more. Once you've satisfied yourself with M91, go about 45 arc minutes due west to M88. M88 is a bit brighter at visual index 4 and has a size of 6 by 3 arc minutes.

You just found four more galaxies. Congratulations! Now, practice. Go back to Vindemiatrix or rho Virg and work your way back to M89 using the above roadmap. From M89, instead of heading north to M90, nudge the scope about 10 arc minutes south and then sweep 1 degree to the west. M87, a visual index 4, 7 by 7 arc minute should be centered in the field of view. Only two more to go. To find them (M86 and M84), starting with M87 centered, go north degree and then sweep west a bit more than 1 degree. The two galaxies should be in your field of view. M86 is the easterly and larger of the two. Both are visual index 4 but M86 is 12 by 9 arc minutes in size, while M84 is 5 by 4.

The following table summarizes these 12 galaxies and their properties.

M Number

Visual Index

RA

DEC

Size (arc min)

Shape (as seen)

M99

4

12h 18.8m

14 deg 25 min

5 x 4

Round

M98

5

12h 13.8m

14 deg 54 min

8 x 2

Streak

M100

5

12hr 22.9m

15 deg 49 min

6 x 5

Round

M60

4

12h 43.7m

11 deg 33 min

7 x 6

Round

M59

4

12h 42m

11 deg 39 min

5 x 4

Round

M58

4

12h 37.7m

11 deg 49 min

6 x 5

Round

M89

4

12h 35.7m

12 deg 33 min

7 x 4

Oval

M90

5

12h 36.8m

13 deg 10 min

11 x 4

Oval

M91

5

12h 35.4m

14 deg 30 min

5 x 4

Round

M88

4

12h 32 m

14 deg 25 min

6 x 4

Oval

M87

4

12h 30.8m

12 deg 23 min

7 x 7

Round

M86

4

12h 26.2m

12 deg 57 min

12 x 9

Oval

M84

4

12h 25.1m

12 deg 53 min

5 x 4

Round

Table 12

The following figure shows a plot of the region containing the thirteen galaxies. Denebola is off the plot, to the right, at DEC 15 degrees, RA 11 hours, 47 min.

Figure 72

Have fun and enjoy hunting the galaxies of Virgo and Leo!

Many thanks to Mark Christensen who authored the “lion’s share” (sorry – couldn’t resist) of this article!