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Old 21-11-2012, 10:23 PM
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5ash
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Length of exposure

How long can you expose a picture before light pollution becomes a problem ? I am of two minds whether to take the step to guided exposures as at present I can get at least 60 % perfect stars for 4 minute exposures at iso 400 using an ed80 on an NEQ6 mount.
Philip
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Old 21-11-2012, 10:28 PM
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mithrandir (Andrew)
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Depends on where you are Philip. Here in outer Sydney 30 secs can be enough for light pollution to flood the image. I'm waiting for a clear night to see if a CLS filter makes much difference.
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Old 22-11-2012, 08:17 AM
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Do a google on "ccd exposure calculator" and it should give quite a few hits. Have a look at this one
http://starizona.com/acb/ccd/calc_ideal.aspx
The basic idea id that you take an exposure, measure the adu of the background and enter exposure time and background levels and the calculator spews out an ideal subframe exposure time.
Geoff
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Old 23-11-2012, 12:34 PM
DJT (David)
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Quote:
Originally Posted by mithrandir View Post
Depends on where you are Philip. Here in outer Sydney 30 secs can be enough for light pollution to flood the image. I'm waiting for a clear night to see if a CLS filter makes much difference.
Hi Andrew

Am able to guide and create 20 minute subs at ISO400 with a CLS filter from just outside of CBD. Prior to CLS, I would blow in 30 seconds..a pointless exercise from my location but you can process it out?
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