#21  
Old 09-05-2016, 07:41 PM
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SkyViking (Rolf)
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Originally Posted by gregbradley View Post
Quite an improvement up to 32hours and then only a bit extra for a lot of extra exposure.
Greg.
I should have linked to the original size version: (http://www.rolfolsenastrophotography...er/i-Sb22cmT/O)
SNR improves significantly with each step, all the way up to 103 hours. The very faintest details are only well defined in the last frame.
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  #22  
Old 10-05-2016, 05:58 AM
jwheel69 (Joe Wheelock)
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Very interesting!
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Old 10-05-2016, 07:14 PM
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Originally Posted by gregbradley View Post
I see QHY have listed some low read noise Sony CMOS sensors. I agree CMOS is likely to be the way of the future at some point. My Sony A7r2 mirrorless camera for example has read noise well under 1 electron per one test. Sony is concentrating on CMOS over CCD so I expect the advances to be more in that area. It would be great to get one of these Sony A7r2 sensors which is backside illuminated with copper circuitry and on chip analogue to digital converters in a mono version. If Sony ever bring out a mono camera like Leica have it could be a good one.
I only just noticed the other day that Leica had produced a mono camera. The Sony A7 were definitely interesting, and I agree, if we saw a mono version of that come out it could be very interesting indeed.

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Originally Posted by gregbradley View Post
I am not sure what intelligent stacking you are referring to as usually its quite simplistic like average or median. I do notice 2 x 2 binning to tends to round out stars as well.
It's more the rejection side of things that I think could improve the integration, rather than the actual average/median itself, but also the ability to be more discerning and discard short frames that are less than ideal and otherwise might have compromised the quality of a longer frame.




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Originally Posted by gregbradley View Post
Its been my experience that small well cameras tend to show more bloated stars to what I think is the outer halo of the airy disc normally dim being brighter. But I think also because there is less bit depth in the star image itself and when you stretch the image the star data can break down more easily. Less so when its got greater depth as in deeper wells. That may not be a correct explanation but I do see my 16803 images as having much more robust stars that stand up to processing better than small well camera stars.

But there are also plenty of examples of excellent images with great stars from small well cameras so perhaps its more about the processing steps.

Greg.
Your experiences seem to gel with what I've noticed, but I'm like you not exactly sure what the cause is.

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Originally Posted by SkyViking View Post
Interesting experiment Lee, always good to see this kind of stuff.
I did a similar comparison of SNR increase as a function of subframes - up to 103 hours: http://www.rolfolsenastrophotography...er/i-Sb22cmT/A
Each step represents roughly double the number of subexposures (mine are 5 mins each)
Thanks Rolf, beautiful example. Loved your work on the Antlia cluster.
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Old 13-05-2016, 03:54 PM
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Slawomir (Suavi)
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I should have linked to the original size version: (http://www.rolfolsenastrophotography...er/i-Sb22cmT/O)
SNR improves significantly with each step, all the way up to 103 hours. The very faintest details are only well defined in the last frame.
Very nice and unique comparison Rolf. Apart from more detail and less noise, images with longer integration have increasingly more depth as well.
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