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Calibration issue with QHY183C/QHY183M QHYCCD QHY183C · Werner Stumpferl · ... · 13 · 629 · 5

WS65 0.90
Werner Stumpferl
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I have both cameras and with both cameras I have issues with calibrating the amp glow. I have made darks for both cameras, same temperature, same offset, same gain (-10°C, Gain 0, Offset 10)
Configurations:
QHY183C / Optolong L-Pro in a filter holder ... no issue
QHY183C / Optolong l-Ultimate in a filter holder ... problem
QHY183M / Optolong L-Pro in ZWO Mini Filterwheel ... no issue
QHY183M / Antlia O3 3nm in ZWO Mini Filterwheel ... problem
QHY183M / Antlia H 4.5nm in ZWO Mini Filterwheel ... problem

So it seems that I have only problems with narrowband filters, independend if Color or Mono Camera.

Software is APP, Scope is a FMA180

All Lights are made with same temperature, gain and offset as darks. And this is the result with both cameras. Last picture is with L-PRo as an example with no issues.

Just for info, I also have a QHY294C, QHY294M, QHY268C, QMY268M, QHY533M ... all with absolute no problems, specially with the QHY294x who have also amp glow, absolute no problem to calibrate them out.
Any ideas from where is comes ?
qhy-1.pngqhy-2.pngqhy-3.pngqhy-4.png
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andreatax 9.89
andrea tasselli
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Calibrating out amp glow with NB is trickier than with BB filters because the background is so much less noticeable. While I don't have a 183 I had a similar issue with one of my cameras and I resolved by tacking a different kind of dark master frame, one incorporating bias offset and matching the temperature to that of the light frames. So my advice to you is to try that.
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WS65 0.90
Werner Stumpferl
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andrea tasselli:
Calibrating out amp glow with NB is trickier than with BB filters because the background is so much less noticeable. While I don't have a 183 I had a similar issue with one of my cameras and I resolved by tacking a different kind of dark master frame, one incorporating bias offset and matching the temperature to that of the light frames. So my advice to you is to try that.

Hi Andrea,

independent that I have never had problems with darks with my several other cameras, what have you done ? You took a master dark with same temperature but other offset ? Or Gain ? And tried as long as you got good enough results ?

CS
Werner
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andreatax 9.89
andrea tasselli
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Werner Stumpferl:
Hi Andrea,

independent that I have never had problems with darks with my several other cameras, what have you done ? You took a master dark with same temperature but other offset ? Or Gain ? And tried as long as you got good enough results ?

CS
Werner


Hi Werner,

I'm taking darks with the same gain and offset as the lights as well as at the same temperature and create the master drak frames without any bias removal. This is done in PI so I can't say whether APP would produce the same results but PI does indeed cleanly remove the amplifier glow.

Andrea
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WS65 0.90
Werner Stumpferl
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APP creates the masterdark also without bias so no difference to PI. And with other cameras I never had this artefacts.
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andreatax 9.89
andrea tasselli
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I can only suggest you put some of the raw darks and lights on a public folder and I and (possibly) others try to replicate the issue or solve it, if it so happens.

Edit: How long were the exposures here?
Edited ...
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WS65 0.90
Werner Stumpferl
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300 sec for each sub, total exposure min. 3 hours.
Today evening I will upload some files in dropbox and will share the link.
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WS65 0.90
Werner Stumpferl
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here is the link to dropbox, 4 Light Frames, 1 Masterdark. Also one result of a stack and calibration of 47x 300sec with below confituration.
Made with a FMA180, QHY183M (Mono) and Antlia O3 3nm Filter.

https://www.dropbox.com/sh/kwwfin1p0w7oiof/AACQajcsRgGsZ8ARIfY88Oa0a?dl=0
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andreatax 9.89
andrea tasselli
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What I actually meant in my previous post is to have raw dark files (like 10) just to make sure there is nothing in the pipeline that might give you the issue you're experiencing. This said I used your master dark and albeit there wasn't an accompanying flat master the light frame seems seem to calibrate just right For what I can see the signal is really weak and the noise pretty large but otherwise nothing untoward imaging it with few more hours (let's say 7-8 hours) to get a decent image.
image.png
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WS65 0.90
Werner Stumpferl
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Hi Andrea, 
I have only the master dark. And if you look at the right side of your calibrated picture you can see very faint the same artefact as in my pictures. The more lights you use the more artefact is visible. 
If you look at other users of the imx183 sensor I can't see any problems whether color nore Mono. And with me it's only visible with narrowband filters, no problem with broadband.
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andreatax 9.89
andrea tasselli
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Hi Werner,

Looking at the final stack I can't see much to distinguish that area from other areas and some have even worse signature than that. Yet the issue with residuals seems to exists with that sensor, see here:

ASI183MM test (astrosurf.com)

Therefore it is important to understand whether this can be calibrated out and therefore the need for raw darks, which you can always produce.
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SickL 0.00
Lutz Kirchner
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Hi Werner,

I purchased the ZWO ASI 183 GT (same sensor as your cam) as a secondary to accompany my ZWO ASI 2600 MM Pro. With the latter I always use bias (aka offset) frames to calibrate my flats. This did not work well with the 183 GT, since (disclaimer: that is my personal assumption) the amp glow effect is visible even in short exposures, such as in flat frames. In a bias frame it is not visible (because super short), hence I would not recommend bias but dark flats instead. Since dark flats are captured with the same settings as the flat frames (gain, exposure time) they work well with my 183 GT and the amp glow is calibrated out effectively. Might be worth a try with you setting.

Good luck and cs, Lutz.

Edit: Since you only have problems with NB filters, which usually need longer exposure times when shooting flats and therefore show a more pronounced amp glow effect, this fact seems to support my assumption.
Edited ...
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WS65 0.90
Werner Stumpferl
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Hi Lutz, 
I have tried all, especially lights only with master dark, no bias, for sure with same temperature, gain and offset. Also single sub is 5min,total exposure more then 3 hours, sometimes up to 16. But only with NB I see this artefact. 
What I try next is to make images not with the FMA180 but with the pro. I give feedback what happens then. 
CS Werner
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SickL 0.00
Lutz Kirchner
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Try dark flats instead of bias to calibrate your flats. That did the trick for me. The dark flat has to have same gain, temperature and exposure time as the flats (which makes shooting them a pita…), e.g. around 500 ms for NB filters. From my experience only when combining the dark flat corrected flat with lights and darks (so, the full scale procedure) the IMX183 is tamed and the amp glow is gone. When I omitted the flats and only used darks and lights, I could not get rid of the amp glow effect.
Changing the scope will do no good, I am afraid. It is all depending on being able to correct for long exposures and the corresponding amp glow in lights *and*  flats.
Looking forward to you reporting back smile Good luck!

PS: Mind me asking why you have so many cams? I already have a guilty conscience while only owning two dedicated astro cams ;)
PPS: I once owned an ASI 296MC. Lots of amp glow but properly corrected with flats/bias. The IMX183 seems very special in this regard…
Edited ...
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