Unexplained hot pixel clusters in live stack.

Discussions of Electronically Assisted Astronomy using the Live Stacking feature.
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Roberto
Posts: 2
Joined: Sun Jan 19, 2020 12:53 am

Unexplained hot pixel clusters in live stack.

Post by Roberto »

Hi,

When I have live view active with 240 sec exposure,with dark and flat to calibrate, there is no noise besides a few hands full of isolated hot pixels. I'm using the histogram stretch of the camera control panel. The stretch is extreme to make the hot pixels visible, the scope cover is on. So far, everything looks pretty good.

The same exposure stored and viewed via folder monitor camera, with same calibration frames and same stretch gives the same result. This is still consistent to me.

However, when I use this same stored exposure in live stack as single frame (via folder monitor), with the same dark and flat files, with the same extreme stretch in the camera control panel, I get significant larger and more hot pixel clusters, and a visible layer background noise. The stretch controls of the live stack histogram are left at default. I get similar result when I reset to camera control panel histogram controls,and use the live stack histogram controls. (slightly more noise though)

Doing live stack with same exposure settings and sensor temperature, I get similar result. Hot pixel clusters and visible background noise. Subsequent stacked frames reduce the background noise as expected. But the hot pixel clusters remain, some of them even grow. The hot pixel clusters are the reason I was looking into this.They show up in the stack and on a bad polar alignment day....

Is there an explanation for this? Is the live stack view at a larger bit depth? I don't mind about the very low level noise, but the hot pixel clusters are really annoying me.

Kind regards,

Rob.
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admin
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Re: Unexplained hot pixel clusters in live stack.

Post by admin »

Hi Rob,

Have you tried adjusting the stretch in the live stack to turn it off by making the yellow line straight – i.e. put the black level to the left, the white level to the right and the grey level bang in the middle. That would mean that only the display histogram stretch should be contributing. If you're still seeing different effects at that point then something odd may be going on (and it would be good to share the frames in use with me via Google Drive or similar for further testing).

Cheers, Robin
Roberto
Posts: 2
Joined: Sun Jan 19, 2020 12:53 am

Re: Unexplained hot pixel clusters in live stack.

Post by Roberto »

Hi Robin,

Thank you for your reply.

Yes I did. Each time I witched histogram controls, I made sure the other was reset to default.

Sorry, I deleted the frame. I'll make a fresh one and share it.

Kind regards,

Rob.
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