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Requesting help with HyperStar image of M3

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#1 ts298

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Posted 18 June 2021 - 10:20 PM

I'm running an unguided C8 HyperStar V4 on an AVX mount with an ASI 294MC pro (cooled) camera, which I switched from the 183MC (non-cooled). With the 183MC I had strong light pollution gradients which I could fix with AstroPixelProcessor, but now that I have the 294MC pro, my images are plagued with artifact, the worst of which is a diffuse paintbrush-like background artifact (walking noise?). I've been working on my setup and technique based on advice given here but I just can't figure out what I'm doing wrong. I would really love for any feedback on this FITS stack. I've hit one of those ruts where I just can't move forward no matter what I think of fixing.

 

 

Things I've done to optimize image quality:

-Tight polar alignment, tight focus with Bhatinov mask
-Remove Optolong L-Pro filter (now shooting with no filter, although I just received a UV/IR cut filter)
-Reduce sub exposure time (now 10s)
-Lengthen flat exposure time to accommodate non-linear response of 294MC pro (3s with dimmed LED light panel); ADU is 19k
-Incorporated dark flats (3s to match flats)
-Stopped using bias frames

 

 

For this image:
Telescope: C8
Reducer: HyperStar (390 mm, f2)
Mount: AVX
Filter: None
Camera: ASI 294MC pro @ -10C, gain: 0
Capture software: ASI Air Pro
Light frames: 369 x 10 s (1 hour)
Dark frames: 20 x 10s
Flat frames: 20 x 3s
Dark flat frames: 20 x 3s
Sky: Bortle 7/8

 

Image: https://drive.google...iew?usp=sharing

 

I'm very frustrated as I've done my best to lock down the fundamentals of image acquisition. Any and all help is greatly appreciated.


Edited by ts298, 18 June 2021 - 10:24 PM.


#2 ts298

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Posted 19 June 2021 - 08:53 AM

To make it easier to look at, I uploaded a rough process of the stack after cropping and removing gradients with APP:

 

https://i.ibb.co/8Xm...-at-9-50-AM.jpg

 

Could the noise be from setting the gain to 0?

 

And does it look like my flats are overcorrecting even with an ADU of 19k?



#3 dswtan

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Posted 19 June 2021 - 10:31 AM

This (whole) thread may help you:

https://www.cloudyni...-in-processing/


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#4 ts298

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Posted 19 June 2021 - 03:22 PM

This (whole) thread may help you:

https://www.cloudyni...-in-processing/

 

Thank you! After reading and thinking through what I may have done, I figured it out. The telescope was badly misbalanced on the declination axis; that explains the walking noise. I'm happy to have figured this out but sad that it means that an otherwise good session can't be salvaged.


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