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Old 11-08-2013, 08:22 AM
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gregbradley
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Join Date: Feb 2006
Location: Sydney
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Yes I think that is the case that a DSLR is more affected by light pollution than a CCD I think its because of ISO on DSLRs. When you hit a certain level of ISO in a DSLR you are above 1:1 amplification whereas CCD the amplification gain as far as I know is very mild and around 1 I think. So if you are above about ISO800 amplification is multiplying everything including the light pollution so it fills up the smaller pixel wells faster than a slower deeper CCD image without that amped up affect. I think it can be demonstrated mathematically as well.

I imaged with a Tak BRC250 from an earlier house that was quite light polluted. It actually did pretty good with an Apogee U16M. I was surprised. That was HaLRGB imaging of things like the Tarantula Neb.

That BRC 250 in hindsight was a beautiful scope. Its F5.

Greg.



Quote:
Originally Posted by DJT View Post
Hi Greg
Thanks for the pointers.

As you point out, it's a camera issue not an optics one. I find I can get around 6 minute subs using a canon with an LP filter and an f7.7 scope before it all goes pear shaped.

So the concern is that getting a very fast scope won't really be a great advantage, just pulling in Sky glow faster unless I am using a ha filter?


Objective is really trying to get a good range of focal lengths for imaging but based on DSLR ahead of going the ccd route. Currently referencing the kit used by Ian cooper on the " imaging the southern sky's" book as I try to figure this out.
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