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Old 26-03-2013, 07:54 AM
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Shiraz (Ray)
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Shiraz is offline
Join Date: Apr 2010
Location: ardrossan south australia
Posts: 4,822
Originally Posted by SpaceNoob View Post
With advice from SBIG I have been using this calculator for my subs:

I have found it useful. You'll need to adjust values to match your actual camera and sky data. Instructions are available on the top of the page.
thanks for the link Chris. Do you use the calculator for narrowband and if so, what sub exposure lengths does it suggest?

Originally Posted by RickS View Post
Hi Ray,

I don't have time to dig through your post in detail right now, unfortunately, but it looks like a very interesting analysis.

In case you haven't seen it before, here's another take on determining optimal sub-exposure length:

thanks Rick - yeah, sorry its so wordy. thanks for the link to the CN article, need to go through it in depth, but it looks quite similar to what I did

Originally Posted by RobF View Post
And reading another post here by Peter Ward, and owning an 8300 chip camera myself, guess the other issue of oversaturation of bright stars on some fields if you go crazy with long NB sub times.....
Yes Rob, seems there is always a tradeoff between headroom and SNR and the systems I looked at all had similar headroom - the 3200 was best. Narrowband should help though - reduces the star brightness by maybe a factor of 30 or more. What sub lengths do you use for narrowband?

regards Ray
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