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Thick Color Bands in Light frames

QHYCCD QHY168C Equipment CMOS Banding
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webcubus avatar
webcubus avatar
I've been running a QHY168C for several years and fairly recently, it seems to have developed mysterious thick bands that appear in some light frames. I've tried a number of power supplies, different outlets in my house, separating the camera power from the rest of the rig (I normally run through DC Hub from DeepSkyDad), and nothing seems to help.

I've got a ticket open with QHY support and all they've offered me so far is to increase the offset. I've been shooting gain 10/offset 50 forever and I confirmed that for bias frames the minimum ADU is 4, so I'm not clipping and this seems like an unlikely fix.

Any other suggestions of things to try/check? The attached light frame is 300s with an IDAS NBZ dual narrowband filter - single sub, no calibration, just an autostretch in PixInsight.
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BryanHudson avatar
BryanHudson avatar
I've had that issue sometimes with stacked images from my ASI2600MC pro. Two things have helped mesmileoing more flat frames and/or running debayer on the image before doing dynamicbackground extraction
TiffsAndAstro avatar
TiffsAndAstro avatar
I've been running a QHY168C for several years and fairly recently, it seems to have developed mysterious thick bands that appear in some light frames. I've tried a number of power supplies, different outlets in my house, separating the camera power from the rest of the rig (I normally run through DC Hub from DeepSkyDad), and nothing seems to help.

I've got a ticket open with QHY support and all they've offered me so far is to increase the offset. I've been shooting gain 10/offset 50 forever and I confirmed that for bias frames the minimum ADU is 4, so I'm not clipping and this seems like an unlikely fix.

Any other suggestions of things to try/check? The attached light frame is 300s with an IDAS NBZ dual narrowband filter - single sub, no calibration, just an autostretch in PixInsight.

looks like the result of strong moonlight. when were these taken? was the moon in the sky like a big pizza pie ?
jmdl101 avatar
jmdl101 avatar
This looks like a completely normal uncalibrated light with the NBZ filter. The green to red gradient should be eliminated with proper flat frames and the background extraction.
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jmdl101 avatar
jmdl101 avatar
Yours looks more like the moon may have caused the gradient looking back at some of my own images. What was the moon phase, was this recent under a bright moon? Here's one of mine from a bright moon night. A single 300s uncalibrated light frame, a heavily stretched master flat, and the final processed image. 
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webcubus avatar
webcubus avatar
Thank you for the responses, but I've shot thousands of subs through the NBZ in various moon phases - this post is not about the gradient or color, which I know are normal. It is about the thick, faint alternating yellow and blue horizontal bands through the image. I've drawn lines to try to highlight them better.
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jmdl101 avatar
jmdl101 avatar
Thank you for the responses, but I've shot thousands of subs through the NBZ in various moon phases - this post is not about the gradient or color, which I know are normal. It is about the thick, faint alternating yellow and blue horizontal bands through the image. I've drawn lines to try to highlight them better.

I didn't even notice those before, sorry about that. Yeah those definitely look like a camera issue, especially if you've tried new cables and power supplies. Can you adjust the usb speed on your camera to a slower transfer speed? I think the few times I've seen people post with similar issues they ended up needing a new usb interface on the camera.
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andrea tasselli avatar
andrea tasselli avatar
What is your bias like, or a dark? If it is the camera amplification/ADC stage you should be able to pick it up with a pretty long dark without cooling. Alternatively shoot with a pinhole camera and no tracking to see what is that like (very low signal, long integration).