Observing report for 13 March 1997




Comet Hale-Bopp


The skies have remained clear at Kitt Peak National Observatory near Tucson the last couple days, except for some cirrus tonight. I've been visually observing the comet every evening and every morning, but I haven't posted for a while because I haven't seen any major changes. However, tonight is the finale to my graduate student "professional" observing career, so I thought I would post a short report from this morning.

Last night was the best observing night of my run with excellent counts on the CCD and <1.5" seeing at my telescope (I'm doing spectroscopy through a 2.1" slit so that's "perfect" seeing for me). Despite the presumably excellent skies, I wasn't seeing quite as faint of stars as I had been and couldn't see the +6.7 star near Polaris that I had been using for a limiting magnitude check. This was probably just fatigue as I was in my 7th straight 14-hour workday. However, I think I was seeing the plasma tail out to 15-16 degrees, with 7-8 degrees on the dust tail which is as good or slightly better than before. In 7x50s, for the first time, I think I was seeing detail in the plasma tail, in the form of one or two dark lanes.

On the guiding system of the 0.9-meter f/31 telescope, I could see some changes in the nuclear area. The guider is not optimized for high-quality viewing, but as others have reported, the psuedo-nucleus appears more star-like than it has. The three arcs I have been seeing didn't appear qualitatively different. The bright jet shooting out to the west was pointing to a smaller P.A. than before, but this could just be an effect of the comet being in a progressively different part of the sky producing a different image rotation in this alt-az telescope. I was still able to guide on the pseudo-nucleus until 15 minutes before sunrise (I didn't try any later than that but the contrast was getting pretty low).

Spectroscopically, the nuclear area is still emitting strongly at the yellow sodium D lines with other emission lines of which I am currently ignorant. What a fluke for a stellar astrophysicist to be in a position to take spectra of a negative magnitude comet!

And soon back to Wyoming and astrophotography and a chance to catch up on sleep this weekend!

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