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Taliesin

QHY183M - Do these dark frames contain too many hot pixels?

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Hi All,

I have a new QHY183M and using this camera for the first time, I have taken 20 dark frames using Sharpcap pro using the capture darks option at unity gain cooled at -5 and -10 degrees at 60 seconds  to create 2 master dark frames. The image when stretched shows a lot of speckles. 

My questions are, is this normal for a CMOS and this particular camera? Are there an unusually large amount of hot pixels?
 

I'd appreciate it if someone could look at them and let me know if this is normal for darks for a sensor like this or whether my sensor has issues. Images are attached. Thank you. 

dark_20_frames_-10.0C_2020-09-08T22_17_51.fits dark_20_frames_-5.1C_2020-09-08T21_39_51.fits

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I downloaded -10C master and first question, why is it only 16 bit?

You stacked 20 subs. Ah, I see - it is SharpCap thing - don't do it. Don't use native drivers - use ASCOM drivers, capture your own darks and stack them yourself to make 32bit calibration masters.

In fact - do all your processing in 32bit.

This number of hot pixels is normal - I counted 16 fully saturated pixels. There is only 7147 pixels that have intensity higher than 50%. Your camera has 5544 x 3684 = 20424096 pixels in total.

7147 is 0.035% of all pixels.

Yes, 0.035% (or 3.5% of a single percent of all pixels) could be considered hot pixels. I would say that is quite normal and in fact - looking at percentages, quite low number of hot pixels.

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Hi Vlaiv,

Thank you for your response And feedback. I’m getting back into AP after a few years and this was just a quick test of the new camera. Ordinarily I would stack them manually in DSS or similar. I was just worried about the number of hot pixels someone had raised concerns so wanted it to be checked out. I’ve also taken note of the driver issue. I have the ascom ones installed but in hurry and haste I just went with whatever it connected at the time but again will ensure things are setup properly. 
 

It was good to hear that my camera hasn’t got too many hot pixels. I’ll be sure to study the images and understand what I’m seeing.

Thanks again 

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