--- UTAHDEB@aol.com wrote:

I have a 135mm Zuiko lens. I thought I'd try and experiment with both lenses.

Actually, the 50mm will give you good shots of how the comet(s) look surrounded by the star-field. Nicely aesthetic, but little comet detail.

How many minutes should I keep the shutter open?

Bracket your exposure times, go from say 1 minute up to 5 minutes. How long the optimum exposure time will be depends on how dark the sky is at your site, and how good your polar alignment and/or guiding is. You probably won't reach the sky-fog limit on your first try unless you were "born to guide". For Hale-Bopp, I shot ASA 200, 400, & 800. I liked the 200 speed shots the best in terms of grain and color. The longest exposures showed the most tail, but 'burned-out' the nucleus. The faster films did not show fainter detail, lending truth to Dave Chamberlain's statement that slow films eventually "catch up" to the fast ones. Dave used to run the 90-inch scope on Kitt Peak, if I may drop a name. With Photoshop, you can scan and digitally combine the best features of several shots.

I guess I'd have to learn hand guiding for anything above 135mm, right?

Comets move with respect to the stars, so I always guide unless the exposure is very short and the comet very bright. Guide on the comet's head, not a background star, or the comet will be smeared. Hand guiding is a piece of cake for 2-to-4 minute exposures. Guide at high power. I currently use an Orion 5mm illuminated cross-hair reticle Plossl and a 2.8x Barlow with my 80mm f/5 guidescope (not the ED). This yields abot 222X, IIRC. When I shot Hale-Bopp I used essentially the same setup except used a 12mm Kellner guiding eyepiece at much lower power. The higher the power, generally the more frequently you make corrections, but they are smaller in degree. I wholeheartedly recommend the Pulseguide illuminator. By pulsing the reticle illumination, you can see your guide target much easier and eye fatigue is considerably lessened. It works with any make of illuminated reticle eyepiece. Try several combinations of exposure times, lenses, guiding vs. not guiding, then change what you did based on the results, for the next time out. Finally, shots taken a few hours apart will make fine stereo pairs. I can loan you my stereo viewer if you get some good pairs. Does any of this help? C. __________________________________ Do you Yahoo!? Win a $20,000 Career Makeover at Yahoo! HotJobs http://hotjobs.sweepstakes.yahoo.com/careermakeover