Decided to go out and get some more photos, on Fuji 1600. It was hard to get well dark-adapted early because there was a surprising amount of traffic. The sky wasn't nearly as transparent as it can be, and the limiting magnitude was worse near the comet than near Polaris. Hyakutake was very near Algol (which was not in eclipse!) and seemed a little fainter (perhaps +2.5 for the comet). In binoculars, the tail was at least 7 degrees long, possibly extending to Delta Persei, which would be about 10 degrees. The bright part of the tail was only a few degrees long. I couldn't see any structure in the tail, but it's still a pretty object in binocs. When I quit, the comet was only about 10 degrees above the horizon.
Posted the following evening:
Just to add some more information to my posting from last night, I got my pictures back this afternoon, and the 50mm shots show an obvious broad tail extending a few degrees, growing fainter and extending a few more degrees. However, on my best three minute exposure, there is also a faint, thin plasma tail extending through Del Per, and continuing through the open cluster NGC 1502 and reaching the edge of the frame about 20 degrees out. The 135mm frames show a little structure in the first part of the tail.
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