Dave-Platt%LADC@CISL-SERVICE-MULTICS.ARPA (Dave Platt) (01/18/86)
The November '85 issue of Sky&Telescope has a column on photographing the comet. Included are some diagrams of a Poncet platform, and hints for using normal-angle lenses such as a 50-55mm (they recommend shooting several stops below full aperture, rather than "wide open", due to the increased amount of detail possible... of course, this requires a sky-tracking platform due to the increased exposure time). The timing figures I gave you (16-30 seconds) are, I admit, pretty low w.r.t. what other folks have been telling you. I'm not sure what the truth of the matter is... I've gotten some pretty decent star photos (with star trails) shooting 30-45 seconds wide-open at f/1.4 with Fuji 1600 color negative film; the results were grainy, but showed a surprising amount of star color (more than the naked eye can pick up under most conditions). I really think that the longer exposure times (5 minutes or so) that other folks suggested would absolutely require a star-tracking platform of some sort... you're going to be shooting a portion of the sky that "moves" very rapidly, and a 5-minute exposure with a fixed camera position would result in an unacceptable blurring of the comet, and probably a total loss of the fine detail in the tail. Another thing to remember. The human eye is FAR better at adapting to widely-differing light levels (in one scene) than any color film available; color photos of the comet will show a much higher contrast than a naked-eye view. Thus, you have the choice of either exposing for detail near the head of the comet, and having most of the tail come out very underexposed (or completely invisible)... or taking a longer exposure to catch detail in the tail of the comet, and having the brighter head "burn" the film into a detail-less white blob. Sigh. I've seen suggestions that people try using variable filters, or performing some darkroom magic by overlaying multiple negative/slide images on one print... but that's probably more than you're going to want to try. All in all, I think your best bet is to go for a standard-lens shot of the comet; bracket heavily by making a whole bunch of exposures, and then choose the best ones to have prints made. Good luck!