QHYCCD Anti "amp glow" function for IMX 174 now extended to very short exposure


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For those as me who are interested in short exposure Deep Sky Imaging, that's
a great new !  ;)

QHYCCD team has heard my "plea" (thanks Qiu !), in order to extend the range of the
anti amp-glow circuit on the QHY174 M (and QHY5III 174 M). Until now, the circuit was
activated at 6 or 7 seconds. And it works fine. But amp glow remains a big problem between
1 to 6 seconds for very short exposures even with cooling and darks substraction.
There is still a part of amp glow which is not removed especially when gain
is set to a high value and incoming signal is vey faint (when using 1 to 5 sec short
exposures). And the faintest stars or galaxies may be "drown" in the parasitic light. 

Now with the software SharpCap 2.9.2936 and last QHYCCD drivers, it becomes possible
to switch on or switch off the circuit for all exposure value, even between 1 to 6 seconds.
And it works fine with darks as shown below. Now skies are cloudy and I'm waiting to try
it on a "real" galaxy with 2 or 3 seconds subs.

Here is a set of 100 darks added with 1,2,3 or 5 seconds exposure. The dynamics of each
pictures are 4x enhanced.
Software : SharpCap 2.9.2936.
QHY174 M cooled at -10°C.
100 darks added.
Gain = 95% (45).
On the left : circuit OFF; on the right : circuit ON



Well, now, QHY174M looks really good.

If i could, i think i should buy one now.



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To illustrate my previous comment a more useful target than only darks, I tried
the Crab nebula M1. In the worst possible conditions: full moon and strong humidity, so
a big drawback, very bright sky as background. Of course, the amp-glow is partially hidden
in background.

A raw unprocessed image to give better idea of the "glowy" skies.
Only 2 seconds exposure...

Now, the comparison with 518 added subs, without dark substraction. Top image is
without anti ampglow circuit. Bottom image is with anti ampglow circuit activated.
Exactly same conditions of shooting and same processing :

Even with very difficult conditions the difference is obvious, anti-amp glow circuit
give a more homogenous and darker background.

And now final result with 518 raw (anti-ampglow Off) plus 4754 raws (anti-ampglow ON) :

Setup :
QHY174 M (-15°C cooled) and 300 Orion Optics F/D 5.3
Gain = 80%.
5272 subs wirth 2 seconds exposure

Registration with DeepSkyStacker
Processing with Iris/Photoshop.
Post processing with Photoshop.

100% Image size.