Christian Skoftland wrote: > What is the minimum exposure for 400 speed slide film at f2.8 that I > should use to photograph the meteors?
Hi Christian, An individual meteor is of short duration -- a fraction of a second to perhaps a few seconds duration in the sky, depending on size of the meteoritic particle, trajectory in the upper atmosphere, etc. Thus, no matter how long your exposure time is, the light from any meteor will only be present for a brief instant. (Kind of like very slow synch speeds in flash photography.) Your minimum shutter speed should be at least as long as the duration of an individual meteor. But catching a single meteor this way is difficult. Chances are that by the time you figure your reaction time and your shutter lag time, much of the light intensity from an individual meteor would be gone. Thus, it's often recommended to go for long exposures. The longer your exposure time, the greater your chances of capturing a meteor on film. Also, the shorter your focal length, the more of the sky you will image, and the greater your chances of capturing a meteor on film. The only disadvantages to very long exposure times is that (a) you will get star trails instead of nice sharp points, and (b) you will get a washed out sky instead of a nice dark sky due to light pollution at your observing site. With a 50mm lens and a fixed-tripod mount, you can typically expose for as long as 20 or 30 seconds before star trailing becomes noticeable. With a 28mm lens and fixed-tripod mount, you can go up to about a minute. If you don't mind a little star-trailing, you may want to just open the shutter and expose for a few minutes. If you're trying to catch a single meteor on film, perhaps you could open the shutter with a cable release, then close it when the first meteor flash appears. Hope this helps. Bill Peifer Rochester, NY - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
