Lake Sonoma Sunday 03 July 2005

by Matthew Marcus


There was a good crowd of ~10 at LSo, where for once, the conditions were near-ideal. It was warm, dry, not very windy, and steady enough for epsilon Lyr to show 4 intermittent Airy disks in my 8".

We started out with planets, four of them including the one we were standing on. Mercury and Venus showed as much detail as one could hope for, that is to say, none. Jupiter was moderatly good, with three moons showing.

Of course, the main event was the comet crash. Doug (the big one, not the other Doug who was there) was very kind about helping people find the thing. It had dimmed since I last saw it in early June. Finally, we all had it, and those with bigger scopes than mine were able to see the galaxy MCG-2-35-10 and tell which was which. I couldn't see the galaxy.

We waited and at last the moment came. And went. Nothing happened. However, after a few minutes, it seemed to the big-scope users that there was a brightening of the central concentration. A bit later, we in the 8" class could definitely make out that there was something stellar appearing in the fuzz. It reminded me of a faint PN with central star, or a galaxy with a stellar nucleus. At first, I wasn't sure if the brightening was real or expectation, especially after Doug reported it to the rest of us.

However, as the night wore on and the object got lower, I became certain that it really had brightened and had done so in a point-like manner. Doug pointed out that since the comet was 88e6 miles away, even if the dust expanded at 6miles/second, a few minutes' worth of expansion would still leave the dust unresolved in the scope.

Figures: Assume his 6mps figure (where'd that come from?) and that we observed it for an hour. That makes a diameter of 2*6*3600=4.32e4 miles. The factor of 2 is due to the distinction between diameter and radius. Now, from 88e6 miles, the subtended angle is 1.7 minutes. The FOV in my scope is something like 20-30', so it would be clearly resolved after an hour, but not after minutes of observation.

After the comet got too low to bother with, we went for the other big event, the SN in M51. We could all see a star in about the right place (1' S of the nucleus, according to a note on TAC). However, we weren't sure that this wasn't a pre-existing star, since old pictures showed stars in the neighborhood.

That was about when people started to leave. I soldiered on, doing first some eye candy as a break from looking at the faint, fuzzy comet, not that M51 wasn't eye-candy. It certainly was! The views of M8, M20, the Veil and M27 in Doug's 17.5" showed detail I've rarely seen, such as thin dark lanes in M27. These objects weren't half-bad in my scope either! After a bit of that, I decided to take my new Herald-Bobroff for a good test-drive by going to well-known objects and seeing what I could find by starhopping from there. I found that if the object was shown with a light outline (not very visible, in their code), it really wasn't very visible! I couldn't see such. I found the scale of the charts to take a bit of getting used to after the much more expanded scale of Uranometria. I did find a few faintish objects, such as 410 and 383/384, all of which I had logged in the past.

The H-B atlas is an impressive piece of work in terms of the amount of information it encodes on objects.

Other atlases show you a nebula. The H-B tells you that it's faint, emission+reflection, irregular and filamentary, and very red, all by various nicks and extensions on the basic box symbol. Similarly, it showed me that a glob in Delphinus (I forget the number) is considered to be of extragalactic origin. When I next go to the Southern Hemisphere, I'm definitely taking it because it covers the whole sky and has special charts for the Magellanic Clouds. On the other hand, the large format makes it a bit unwieldy at the scope, and the C-series charts, which are the deepest which cover the whole sky, could use more stars in places. They'd get too crowded in other places, so I suspect that variable magnitude limits would be a good thing, as they have in the D-series charts.

I hacked around in this manner for a while until I started hearing odd and somewhat scary noises, which were due to garbage-can raids by raccoons. When I shone my flashlight at them, they just looked at me as if to say, "Yes? You want something?". Also, I started to notice the sky getting kind of light. I took a quick peek at Mars, the Pleiades (still pretty even against a bright background) and the rising thin crescent moon, and packed up at ~4:30. I hadn't done an all-nighter there in ages because conditions didn't merit it. This time, although I didn't log many new objects, I did get lots of time under the stars in pleasant conditions with great company.

Can't ask for more!


Posted on sf-bay-tac Jul 04, 2005 16:37:49 PT
Converted by report.pm 1.2 Sep 28, 2005 19:55:43 PT