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Old 06-09-2009, 08:24 PM
Hagar (Doug)
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Hagar is offline
Join Date: Oct 2006
Location: Australia
Posts: 4,646
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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