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Old 07-02-2014, 12:54 AM
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Shiraz (Ray)
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Shiraz is offline
Join Date: Apr 2010
Location: ardrossan south australia
Posts: 4,824
Originally Posted by stevous67 View Post

Thanks Alistair for helping a lot of us with your data. Nice topic Ray, I'll just have to read it once or twenty times just to be sure. It's been very helpful and interesting.


thanks Steve.

Rats, I was hoping that this would be easy to use - big problem is I have a tendency to rabbit on a bit and obscure what I am trying to say. The basic idea is very straightforward - do the calculation once and then aim for the targetADU value thereafter. Used it myself last night - really is dead easy. My camera has a targetADU of about 2150 and I got about a 2100 sky from 5 minute subs - close enough and gave good results.

Originally Posted by alistairsam View Post
Thanks to Ray and Fred
I'm the same Steve, kept it for a "quiet read" atleast 20 times.

One more thing I wanted to ask was about well depth.
After this calc, we aim at reaching the target adu, but how do we deal with shallow well depth sensors like the 8300. 2x2 is not a good option for this and long exposures with rgb tend to saturate the stars rendering it almost colourless.
Any tips?

Rolf gets some amazing colours with his qsi which has the same sensor but his filters are the asronomiks I believe.
Any suggestions

You can actually ignore well depth - it is taken care of automatically and you get an optimised combination of noise and dynamic range by aiming for the targetADU. If you really want more dynamic range, use shorter subs and image for a bit longer overall. Typical cameras will have targetADUs (for the background sky) of 1000-2000 + bias and they all have a top of ~65000 ADU, so the dynamic ranges will be similar - most cameras have dynamic ranges of about 70dB, regardless of the well depth, since those that have large wells also have higher read noise. The cameras with low read noise need shorter exposures than high read noise cameras, but the targetADU method takes care of all that for you. You really do not have to do anything more to get good sub exposures.

not sure what binning does - will give it some thought.

Last edited by Shiraz; 07-02-2014 at 01:17 AM.
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