Observing report for 18 March 1997




Comet Hale-Bopp


"Yes!!!", I exclaimed, leafing through the freshly printed photos at a local photo shop this afternoon. But first, the observing report. It was a great night in the Laramie Valley, as the evening cloudiness cleared after midnight just as forecast. I reached my regular observing site at about 10:20UT (3:20am), with the comet already an obvious beacon in the northeast even only 8 degrees off the deck. I quickly set up the tripod and barndoor mount and polar aligned. I decided to start shooting early since the transparency was excellent. In fact, early on, I may have glimpsed a +7.1 star near Polaris naked-eye. I was definately seeing to at least +6.7; I'll compromise and call it +6.9. The temperature was around freezing and there was an occasional light breeze.

Once the comet got higher, I could definately see the plasma tail out to 15 degrees with a possible extention out the opposite side of the Milky Way to 20 degrees, and the dust tail was definately visible to 8 degrees with a possible extension to 12 degrees. The plasma tail appeared curved, which I've noticed before. Without any extinction correction, a naked-eye "out-out" test without my glasses showed that the coma was significantly brighter than Vega, so the comet must be getting close to -1.

The photos came out great! I was shooting the wonderful Kodak Pro 400 (PPF) using my 58mm and 135mm lenses and I've posted 5 photos to my astrophotography page. If you've looked at my previous Hale-Bopp photos, these new ones are far and away better mainly because they were exposed longer and the sky was so good. The photos confirmed the gentle curve of the plasma tail. This seems rather unusual for a comet, but I suppose the tail is physically so long that there is a substantial travel time for the charged particles to reach the end of the tail, and thus the far part of the tail "lags behind". Although hard to see in the digital images, the prints from the 135mm shots definately show some "feathery" structure in the dust tail, sort of like Comet West, just not as obvious. There is also plasma tail structure visible on the prints that is marginal on the scans.

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