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Old 25-04-2008, 12:22 AM
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PeterO
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Location: Traralgon Vic
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F numbers

Hi all,

Just got my 400d and been playing around with the bulb setting( I made my own cable with a opto isolator). I notice on the pics in the imaging section of the forum that everyone states thier iso and shutter speed but not the F number, am I missing something here?

cheers peter
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Old 25-04-2008, 12:47 AM
Zuts
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Quote:
Originally Posted by PeterO View Post
Hi all,

Just got my 400d and been playing around with the bulb setting( I made my own cable with a opto isolator). I notice on the pics in the imaging section of the forum that everyone states thier iso and shutter speed but not the F number, am I missing something here?

cheers peter
Hi Pete

Most of the photos you see are taken at prime focus. This means any lenses are removed from the camera and the body is plugged into the focusser of the telescope. Therefore the 'F number' in this case depends on the scope used which could be a 14 inch SCT say 4 meter focal length or a 60 mm refractor say 400 mm focal length.

So people usually list the scope and then say how long the shutter was open, say 30 seconds to 30 minutes with good tracking and the ISO.

Paul
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