Observing report for 9 March 1997




Comet Hale-Bopp


I'm up at Kitt Peak National Observatory on my last run for my thesis data. My observations are from about the 6700ft level on the mountain, which is aboue 30 miles west of Tucson. The first two nights of the run suffered from some cirrus clouds which were worse looking east, but night three was clear.

I hadn't seen the comet in clear, dark skies in about three weeks so I was expecting to see a much more spectacular comet than I had previously seen. I wasn't disappointed! My naked-eye limiting magnitude at Polaris (KPNO is at latitude +32) was about +6.7 and the shape of the North America Nebula was quite evident in 7x50s. I didn't have time to get perfectly dark-adapted and light pollution from Tucson was interfering a bit. However, I could trace out the plasma tail to about 15 degrees naked-eye, and the dust tail to about 8 degrees. The dust tail was very neat in binoculars as the denser part nearest the plasma tail gave a 3-D appearance, like looking at a veil or a sheer curtain. The head of the comet was *very* bright; I didn't make a concerted effort at a magnitude estimate and in fact, when I removed my glasses to do a naked-eye "out-out" test, the visible part of the coma was much larger than the out of focus images of the Summer Triangle stars.

My observing project has nothing to do with the comet, but it seemed silly not to try to get a few observations. My telescope is a 0.9-meter unobstructed design used to feed the 2.1-meter telescope's Coude focus spectrograph without using the 2.1-meter telescope, and I'm doing high spectral resolution spectroscopy. You can actually easily look through the telescope, a throwback to the pre-electronic guiding days. In addition to being unobstructed, it also operates at f/30 (I can take data on a 1st magnitude star at sunset!). I couldn't quite get the eyepiece into perfect focus and I only lingered long enough to get the pseudo-nucleus centered, but I could see two concentric "hoods" or "shells" or whatever, which were very impressive. I have no idea as to the magnification; it uses a 4" barrel eyepiece and presumably the eyepiece is of very long focal length. I think the field of view is something like 5-10 arcminutes. If I had to guess, I would say that the magnification is 200 or more (it would have to be with a telescope focal length of 27 meters!). I've got 5 more morning to go and maybe I'll find out more about the setup.

BTW, the spectra were really cool!

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