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Old 06-09-2009, 07:24 PM
Hagar (Doug)
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I think this whole thread has gone way beyond the normal with regard to dark framed images. The original post of dark frames was in fact just to point out the small amount of hot pixels which are present in a NORMAL and I mean NORMAL Dark frame. Not a frame that has been stretched until all pixels are displayed as white, well almost all. If we were to take each pixel on a scale with reality in mind we would find the diference in the ADU/e count to be very similar.

Marc made a very valid point when stating that it is possible to make a dark look like whatever we want and to stretch a dark to the extent as indicated above is way beyond what would be considered normal or constructive.

The reality is that I doubt any camera on the market could stand the amount of stretching displayed here and perform anywhere near as good. The Sony CCD in the QHY8 has dark currents well below almost all Kodak CCD used in Astro cameras and without doubt less bright pixels than the Kodak range.

What must be remembered in all this is that some have higher sensitivity, some lower dark noise and some better single colour response. The choise is a personal one and one based on your own requirements.

I posted the darks purely to show prospective purchasers what they can expect from the QHY8 camera with respect to dark noise. I have been asked this question on numerous occasions by PM and email and my response has always been the same." In most cases there is no real need for dark frames but if you want a very small lift in image quality and I mean very small then it is worth making a library of darks and using them."
I have such a library and use it in most cases but don't for some where bias frames are enough.

I hope this post explains what was meant by thread and helps someone make up their mind on a great camera which can produce some great results. Don't expect miracles with any camera, even the most expensive can produce junk. Imaging is a matter of a lot of influences and not just the camera, focus, processing, exposure time, registration and collating and things like seeing conditions all add up to final image quality.

Good luck with your imaging Guy's, Have fun.
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  #22  
Old 08-09-2009, 09:58 PM
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marki
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Have to agree with Doug here. The camera generates very little dark current, so little in fact I often don't bother with dark frames (flats yes due to dirty glass ). Marc I have never had a dark frame look like that in nearly two years of owning a QHY8. Perhaps you streched it so much it ripped in two .

Mark
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  #23  
Old 09-09-2009, 06:19 AM
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multiweb (Marc)
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Quote:
Originally Posted by marki View Post
Have to agree with Doug here. The camera generates very little dark current, so little in fact I often don't bother with dark frames (flats yes due to dirty glass ). Marc I have never had a dark frame look like that in nearly two years of owning a QHY8. Perhaps you streched it so much it ripped in two .

Mark
This thread is till going? If you do flat fielding you do need to shoot bias to scale them correctly. So if you looked into your bias levels and inspect them you would see similar patterns.
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  #24  
Old 09-09-2009, 07:56 AM
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The original dark posted looked pretty fine to me.

Here is one from my FLI ML8300 at -40C 600 seconds. Not much noise but there is a pattern noise. The Kodak 8300 chip seems to be a real winner and more and more great images are coming from them in various manufacturer's cameras. Kodak really got it right with this one.

Little bit of amp glow top left otherwise very very clean and perfect. You won't see darks this perfect from many chips.
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  #25  
Old 09-09-2009, 06:05 PM
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Greg's correct, Kodak really pulled their socks up on this new sensor.
But all the newer CCD's from Kodak are performing better than the first gen, but thats to be expected, technology moves in one direction.
Even in warmer temps, the Kodak sensors being pumped out seem to have better dark signal.


Theo
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  #26  
Old 09-09-2009, 10:31 PM
Prickly
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Hi Doug,

Good luck with the new ccd. The QHY8 certainly is a very nice ccd and hard to beat for the size and price in my view (no affiliations here either). I have had the chance to use one on my scope once and it really was great.

Hard to tell how stretched some of those images are and what this means in a practical sense - from my recollection with Kens QHY8 there was very little noise apparent in the images we obtained and I gather Ken rarely bothered with darks. Proof of the pudding is in the eating - look forward to seeing some nice shots.

Clear skies and happy shooting.
David
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