Understanding zero amp glow

[Ratlet]

I'm hoping someone can help me here.  I've been playing around with my hypercam 533C which uses the IMX533 sensor.  As I understand it this sensor is zero amp glow.

I've been building a dark library at various temperatures and exposure times.  On stacking my darks in siril to build a master dark I used the auto stretch function to just see what it looked like and I was a bit surprised that there was a very clear glow in one corner.  Is this normal?  I've attached a single 300s exposure taken at -10C below with the siril auto stretch applied and it shows a small, but clear bright spot in the corner.  My feeling is that this isn't a problem really and it's just an artifact on there being so little brightness in the image that the auto stretch is having to stretch the image phenomenally hard and giving the impression of an issue.  I've also attached a snip of an autostretched stack of 20x180s darks at -5C

I'll add that the unstretched dark is completely black and I've got zero issues with the camera so far.  I guess it is just a gap in my understanding of zero amp glow.

Thanks!

[Clarkey]

I don't know how severely stretched that image is, but I am not sure 'zero' really exists. However, that does look like a pretty clear 'glow'. I assume there was absolutely no light leakage possible?

[Ratlet]

47 minutes ago, Clarkey said:

I don't know how severely stretched that image is, but I am not sure 'zero' really exists. However, that does look like a pretty clear 'glow'. I assume there was absolutely no light leakage possible?

I don't see anyway as the sensor has a cap and bung installed.  Unless the light is getting in from behind the sensor, but that seems unlikely.

I tend to agree with yout about whether true zero glow exists.

[ONIKKINEN]

Does look like some amp glow. Maybe ask the manufacturer if everything is ok with the camera? Could be some kind of fault. As far as i understand the ampglow comes from the circuitry in the camera and not necessarily the sensor itself, but thats a wild guess at best.

I know these new Sony starvis sensors are quoted as completely amp glow free, but my 571 sensor camera (made by touptek, as is the hypercam i presume) has a little bit of extra glow visible at the top of the frame in extreme darks. By extreme i mean 3600s darks running for 15 hours at room temperature with the cooler at 90%+ power all of that time, but still there is some.

[Ratlet]

8 hours ago, ONIKKINEN said:

Does look like some amp glow. Maybe ask the manufacturer if everything is ok with the camera? Could be some kind of fault. As far as i understand the ampglow comes from the circuitry in the camera and not necessarily the sensor itself, but thats a wild guess at best.

I know these new Sony starvis sensors are quoted as completely amp glow free, but my 571 sensor camera (made by touptek, as is the hypercam i presume) has a little bit of extra glow visible at the top of the frame in extreme darks. By extreme i mean 3600s darks running for 15 hours at room temperature with the cooler at 90%+ power all of that time, but still there is some.

I've raised a ticket with Altair about it.  The camera functions very well and I've very happy with the performance, but that doesn't mean that there isn't a fault. or that it won't get worse.  I've managed to find some dark frames from ZWO ASI533mc and they do not show the amp glow under autostretch so it's either a function of the design of the camera and it's not quite zero amp glow or its got a fault.

I've also spoken to some guys on cloudy nights who have shared their darks from the asi533c at the length and temp and they have no glow, all compared in asi fitsviewer with autostretch.  The Altair site also says the sensor should be free of glows of any kind which is not encouraging.

Edit: I'm back home now and have loaded up all my lights from 4 different targets.  They are all 90s exposures.  I cannot see any sign of the glow at all.  I've tried with siril autostretch and the asi viewer and there is no sign of it.

Edited October 14, 2022 by Ratlet

[Ratlet]

I'm going to attach my stacked dark frame from the Altair Astro Hypercam 533C in the hope that someone can provide some insight as I don't think that snips of the autostretch are being useful.  My suspicion is that it is to do with the way that the Altair handles the data versus how the ASI533C handles it and that in a real world situation the signal from it is essentially non existent.   I'm going to wait for Altair to get back to me and see what they say and also hope that someone who actually understands imaging and data and such can look at it and provide more insight

300s -10C_stacked.fit

[Starflyer]

Have you tried reshooting a dark with the camera on in a totally dark place?  I get a slight light leak on my QHY268M when shooting darks in a light room, I guess it's at a joint somewhere between the camera, filter wheel, OAG etc.

[Ratlet]

1 minute ago, Starflyer said:

Have you tried reshooting a dark with the camera on in a totally dark place?  I get a slight light leak on my QHY268M when shooting darks in a light room, I guess it's at a joint somewhere between the camera, filter wheel, OAG etc.

Yeah, I tried imaging with it in it's peli case with a jacket over it.  Same thing.