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Old Aug 26, 2006, 6:14 AM   #1
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This Lense

OR would it simply be too slow even with a long (30 second) exposure?

Also I can't seem to find it in the documentation but does a Rebel XT have a Bulb or shutter hold open mode to allow me exposures longer than 30 seconds?
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Old Aug 26, 2006, 8:09 AM   #2
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It'll work - If you looks at most telescopes they are mostly f/8 or higher anyway...
Plus if the light is reflected from the sun, it tends to be as bright: http://www.stevesforums.com/forums/v...mp;forum_id=37

BTW I don't know of any dSLR which do not have a bulb position :idea:
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Old Aug 27, 2006, 1:51 PM   #3
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It would work. I don't do astrophotography, but most people who do seem to use telescopes, though. (Astrophotography doesn't need the f/stops or close focusing capability of a regular telehoto lens.)

If you've lost your manual, Canon has it available for download as an Adobe Acrobat file.

The bulb mode is described on p. 93. (It works best with a remote shutter release, like the RS60-E3 ).

The mirror lockup mode (good for reducing vibraion produced by the flip mirror) is described on p. 94.

The long exposure noise reduction is described on p. 148. (It's not really explained, but I believe that the camera takes a dark frame with the shutter closed, and subtracts it from the exposure. The dark frame takes as long as the exposure to capture.)

You might also consider stacking software. Registax is a freeware program that is widely used.
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