Comet 73P Schwassmann-Wachmann 3

by Bob Jardine

Observing Report -- Cupertino -- 9 May 2006 (Tuesday AM)

Comet 73P Schwassmann-Wachmann 3

Thanks to Dennis Beckley for his two reports from the night before -- they provided inspiration to get past my inertia and the "it's almost full-moon, so there can't be any observing" default behavior.

I'd seen comet 73P a few times in April -- always the C fragment until I was at Anderson Mesa in late April, and Bill Ferris provided a chart of the other components. At that time, the C fragment was definitely by far brighter, although both B and C could be spotted with binoculars. As Dennis said, B is now significantly brighter.

I set the alarm clock for 4:00 AM. There was only a short window between moonset and astronomical twilight. I grabbed a red flashlight left on the nightstand, my binoculars, and the chart I had printed from SNP (showing four fragments: B, C, G, and R).

Both fragments B and C were easy to find (I didn't look for G and R). B was in the same FOV as Vega. C was just one FOV away from Alberio. Both nearly overhead, so I observed lying on my back on the deck.

Fragment B: Obvious, bright, large. At first, just round, with brighter (but not stellar) center. Eventually, I teased out a very dim tail, but it was large -- almost 1/3 of the FOV. IIRC, that FOV is about 3.5 degrees, so the tail was easily 1.5 degrees. And this was with just binocs in a very light-polluted sky.

Fragment C: Formerly the brightest one, now dimmer than B. But still very easy. Similar to B, but significantly smaller and dimmer. Brighter center, but again not quite stellar. I just imagined a short tail, same PA as B's tail, but 1/2 the length, or less (maybe 1/5 or 1/6 the FOV). The tail points right at M56 !

M56: It was important to locate M56, because they were so close and could have been confused. M56 was barely visible, smaller and dimmer than Fragment C of 73P. Mostly visible only with AV, I could hold it directly only occasionally. I had seen M56 with binocs from a darker sky, but this was the first time I can remember seeing it from home.

M27: This was nice. A roundish fuzzball, pretty large (larger than M56), easy to hold with direct vision. Dimmer than Fragment C, but brighter than M56.

It was 4:30; time to get back to bed. SQM read 18.93, 18.97. I didn't take time to do a careful visual estimate, but I'd call it around mag 4.5, given that I could see only the four brightest stars in Sagitta.

Very cool to see (effectively) two comets at the same time. And to see this comet move so fast (only two weeks ago it was in CrB) and change so much.

Joe Bob sez: 73P: check it out while you can! I've read that this one might not survive this trip around the sun.

Posted on sf-bay-tac May 09, 2006 10:47:05 PT
Converted by report.pm 1.4 Jul 18, 2006 17:39:23 PT