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Rolling Shutter with ZWO ASI533MC Pro?

ZWO ASI533MC Pro Optolong L-Ultimate Artifacts Troubleshooting
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Ryan Faulkner avatar
Ryan Faulkner avatar
Last night I had this noticeable line in a stretched fits file (this is the Dolphin's Head nebula) using the Optolong L-Ultimate filter. After moving to M42 to try some test exposures with different filters, I couldn't see the issue and I went back to the Dolphin's Head and the 2 hours of images I took don't have this issue. When doing flats this morning, I see the same issue again.


This looks like a rolling shutter issue to me. Has anyone else had a similar issue?
The one thing I did not try this morning when doing flats was to switch USB ports. Maybe transfer rate is causing an issue?
My initial stack looks okay, and background extraction and cropping will take care of this, but I don't usually see this.

Any ideas? Thank you in advance.
Johannes Maximilian Möslein avatar
Johannes Maximilian Möslein avatar
I have the 533MM Pro. My Bias frames or short exposures have noticeable lines in them, it's just a characteristic of sensors when you image in low light.
Can you see more of these sensor lines when you stretch more aggressively? Could it have been a trail of a plane or something like that?
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Sean Mc avatar
Sean Mc avatar
You typically don’t get rolling shutter effects unless the camera and/or subject are moving
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Remco avatar
Remco avatar
I think it's something else.
The ASI533 can absolutely suffer from the rolling sensor read-out, but only during very short exposures.
And usually, when the image signal has a different refresh rate, imagine the LEDs from a flat panel refreshing at a different rate. And then you can see some diagonal banding in your flats, But only mildly and at different places in the image every time. 

Looking at the consistency, this to me looks a lot more like a shadow is forming somewhere in your imagetrain.

For reference here are some examples of my shortest flats hyperstretched in PixInsight:
All the way on the left my very shortest flat 0.012 sec. You can see a hint of banding due to the LEDs in my panel refreshing before the image was done.
In the middle 0.014 sec. I'ts completely gone.
On the right a way longer flat frame 19 secs. For when I use my L-Extreme filter. 
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