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Old 21-01-2013, 07:00 PM
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CapturingTheNight (Greg)
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Join Date: Jul 2011
Location: Holbrook, NSW
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Ah yes the good old "600 Rule". I have a blog post here http://www.capturingthenight.com/blog/?p=12 on how I use it for my fixed tripod night sky scapes. Personally I use 500 or less when imaging. It's not perfect as stated, but it's a pretty good guide.

Quote:
Originally Posted by AstroJunk View Post
To be fair though, I had done 600/8 = 75 and thought that was such an absurd number that it couldn't be true...
With your new 650D being a non frame camera then you need to factor that into the equation as well Jonathon, but yeah you don't need to worry about the aperture. Canon's crop factor is 1.6, so with your 8mm it is effectively (for the purpose of the 600 Rule) 12.8mm (8 times 1.6). 600/12.8= 46.8 seconds maximum shutter speed before the stars trail too much to be really noticeable. As I said I tend to do the 500 rule or less. 500/12.8= 39 seconds but for that lens I would just stick it on 30 seconds.
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