Just looked at my 16803 master dark frame and noticed some thing weird. Does it looks like blooming in dark? The hot pixels are far from saturation. It is -20C 600s master dark frame.
What is trailing charge? Does it require hardware fix, firmware update or can be calibrated out? Serial number is STX16803 16060001.
It means that some of the charge is trailing behind when you clock out the sensor. The test data from when it was built in 2016 all looks good. It may require a hardware fix. Please contact Bill at SBIG Service & Repair. bill at sbig dot com.
Does it mean the same artifact will be seen in light frame for brighter stars? I have not done long exposure so I have not seen it. Is it a complicated hardware fix?
Yes it is possible that you would see it on bright, tightly focused stars. Hard to say what the fix is without knowing what is wrong; there are several possible causes. It may need to be repaired, though it is possible that a clock voltage needs to be adjusted.
I guess you'll have to decide for yourself whether it is affecting your imaging or not. I couldn't do any quantitative measurements on it because you uploaded a JPEG. I'd need a FITS file for that.
I uploaded master dark, master bias and a dark sub (-20C, 600s) in the following directory. https://drive.google.com/drive/folders/1UNU6u4_Hs-m92OttNkw5rIE1TGL04phK STX16803_16060001_Bias_M20C: master bias STX16803_16060001_Dark_M20C_600s: master dark STX16803_16060001_600sec_1x1_M20C_600s_0010: dark sub Thanks for your support.
Unfortunately those images were all processed in PixInsight, so I can't use them. I need RAW frames directly from the camera. There's no way to know. If it's a hardware failure it could become progressively worse... or not. It depends on what failed.
The unprocessed dark frame you sent me comes in at 1.2% horizontal trailing charge. It's actually within our specs. It just looks bad when you stack a lot of frames. Can you upload an unprocessed light frame?
Doug, Thanks! What is the spec value? Is 1.2% more typical? Does it help if I send the CCD to Bill to improve it? I have not done long exposure yet. How long should be the light frame exposure?
And do you have measured value when it was manufactured? Did it degrade over time? I am asking because if it falls out spec later and I send CCD for repair, then it may be out of warranty.
The camera was purchased new about 2 years ago. I used another 16803 and it did not look this, I could hardly see any trailing. So is 1.2% typical or much worse than typical? Shall I send the camera for checkup and tuning?
Okay, I found your camera's history. We shipped it to Oceanside in June 2016. I know they don't worry about selling old stock first, but that's a long time sitting on the shelf! 1.2% is typical, though it's usually shorter and brighter rather than longer and fainter. Each sensor has a unique character! It's very faint. If you can't see this in your final calibrated images, I would not worry about it. If you want to send your camera in, we can try to tweak the horizontal clock voltages slightly to reduce the effect. It's up to you.
Thanks! That explains what I saw in another 16803. What should be the light frame exposure time I should use to check for this affect? And which filter?
Filter shouldn't matter. Just use the camera normally, and examine your calibrated and stacked frames critically. You shouldn't be able to see anything. Look at the right-hand side of the brighter stars.