by William Cone
Two of the daunting aspects of this region for the first time observer is the density of objects in a small area, and a lack of bright stars nearby. A simple way to tease apart all those galaxies is to start your work with a larger chart. Sky Atlas 2000 has an enlarged chart of the Virgo Galaxy cluster in the back of the Atlas that I used. It is plotted on a 1 degree grid, each degree being an inch in width. Plenty of breathing room between objects now, and the stars are plotted down to 10.5 magnitudes. A 50mm finderscope can see to about 10th magnitude, so now there are stars on the chart that you can steer by, even if you can't see them with your naked eye. On this chart, my finderscope field of view (5.4 degrees) was huge. In fact it covered most of what I was planning to observe the entire evening. It's a funny feeling to be incrementally adjusting the scope to re-aim at another target, and never actually see the target in the field, until you get to the main eyepiece. After a few hours of this, though, I got used to it. Now that I think of it, using a Telrad is like that for the most part, so maybe it's not so odd after all.
As a newcomer to this region, my strategy was to go after the Messier galaxies. Based on my experiences in Leo, I knew they would generally be larger and/or brighter than the ngc ones. I expected see plenty of ngc galaxies on the way, and in the same field as the M's. They can also help you identify which galaxies are which in a field. Once I've got the lay of the land, I can go back again with more confidence and target the dimmer ones I didn't get to.
The next step was to figure a way in. I had already worked my way over from 6 Com B to m91, the evening before, and it positioned me less than a degree West of a 1 degree bent line of 3 stars running N-S of about 7.5 magnitude. South of that simple asterism is a curving chain of galaxies mixed with a few stars to help guide the way, from m91, all the way to m60. I could then backtrack to m58, hop over to m87, then to the cluster of galaxies around m86 and m84. The reason I didn't go the m86/84 complex first was that it just looked too crowded, and I reasoned I would have an easier time figuring what I was seeing with fewer galaxies in the field to start with.
I then wrote out a list of galaxies I wanted to view, in the order I planned to see them, with a distance measured in degrees, a compass designation, and sometimes a clock position, like this: m58: 1 deg. SE (7:00) from m89 m59: 1.25 deg. E (8:00) from m58 etc.
And it worked! As I mentioned earlier, most everything I went after was in the same finderscope field of view, so I just made minor steering adjustments in the finderscope to triangulate visible stars with the position of the galaxy. In these close quarters, it's pretty easy to land the object in the main eyepiece field, and your guide stars are always there in the finderscope to work off of. I was very cautious and slow as some of the guide stars were dim, even in the finderscope, but they matched the chart well. As I got a bit more confident, I used my own written directions, as noted above, to hop directly from one galaxy to another. Here's my observing notes, though my focus that night was more on navigation than scrutiny of each object.
| M90 | Elongated N-S |
|---|---|
| M89 | round glow. Can see in the same f.o.v. as M90 |
| M58 | Stellar core |
| M59, M60, ngc 4647, ngc 4638 | 76x These are all visible in the same field in a 15mm panoptic. I took the time to sketch this one. ngc 4647 is nestled against M60 at the E. end of the field. M59 is at the W. end. 4638 sits midway in the field, to the south of the center. |
| M87 | Stellar core. Round. ngc 4478 is in the same field to the W. |
| M84, M86, ngc 4388, 4387, 4402, 4438, 4435 | This doesn't even cover the whole neighborhood of this incredible grouping, but it is what showed up in my eyepiece. I wasn't quite prepared for that many galaxies in one field. I just stared and stared, and a few more started popping up with averted vision. The main structural sense of the field to my eyes was a narrow 'Y' form, like the constellation Saggita, with m84 at the bottom, m86 in the center, and 4438, 4435 as the narrow 'y' split at the top. There was also an equilateral triangle formed by M86, M84, and 4388 to the South. In the center of that triangle lay 4387. 4402 was a dim glow NE of M86. It was late, and I was getting dewed out pretty bad, so I sketched the field carefully, to identify the members later. I was glad I saved it for last, as it was a pretty magnificent sight. |
Can't wait to go back! There's 2 more more Messiers further south, and plenty of the ngc's everywhere.
Posted on sf-bay-tac Feb 28, 2006 00:53:12 PT
Converted by report.pm 1.2 Mar 02, 2006 19:57:41 PT