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AMP Glow on ASI 071 Pro

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#1 aashish

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Posted 27 May 2020 - 01:15 AM

I wanted to check and confirm if what I am seeing here is amp glow?

 

This is my first CMOS camera so I am unsure -- I expected there to be none on the ASI 071 MC Pro

 

dark_integration(2).jpg

 

This is at -5C about 5 300s frames stacked. I changed USB cables and its still there -- I even changed camera orientation to rule out light bleed.

Shorter exposures do not seem to show it.

 

Thanks!



#2 sg6

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Posted 27 May 2020 - 02:15 AM

Looks a bit different to the "glow on one side" that is usually shown. But as there is an amp on each pixel I would have expected a more overall "glow".

 

CMOS likely doesn't need 300 seconds and as you say it doesn't appear on shorter exposures, so use shorter exposures. We still seem to apply long long exposure CCD rules to a CMOS that is different technology. Change your thinking.

 

All the "Pro" versions did was reduce ampglow, then AP'ers upped the exposure times to reinstate amp glow. Then complained. Presently seem 2 ZWO's that say "No amp glow" and appear to deliver. However I have little doubt that someone will manage to still achieve some. Lets face it just leave it running for an hour or two and something will go wrong and I do expect someone to try.

 

Imaging course said that something like 2 min 40 sec CMOS was equivalent to around 10+ minutes CCD. Go for 150 sec, maybe 180 sec and just get more exposures.

 

Answer seems obvious: Change thinking from CCD technology, use CMOS technology to your advantage, make use of shorter exposures being adaquate, take shorter exposures and so avoid amp glow.

 

Look at stars under long exposure CMOS images, they are all "WHITE". No color at all, all blown out. That is too long an exposure. Color in stars tends to be one of the first things I look for/at. Most have none these days.


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#3 cuivienor

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Posted 27 May 2020 - 03:35 AM

Do you have a Newt? This looks like what happens with an uncovered back mirror - and maybe the same pattern even with rotation. Have you tried with just the camera and its cover, in a dark place?
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#4 OldManSky

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Posted 27 May 2020 - 08:21 AM

Yeah, that doesn't look like any amp glow I've ever seen.  Like cuivienor said, it looks like a light leak.

Below is a shot grabbed from the web of "typical" 071 amp glow, highly stretched.  

I would investigate light leaks in your dark frame setup.

 

 

Attached Thumbnails

  • asi071_ampglow.jpg

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#5 aashish

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Posted 27 May 2020 - 12:01 PM

Looks a bit different to the "glow on one side" that is usually shown. But as there is an amp on each pixel I would have expected a more overall "glow".

 

CMOS likely doesn't need 300 seconds and as you say it doesn't appear on shorter exposures, so use shorter exposures. We still seem to apply long long exposure CCD rules to a CMOS that is different technology. Change your thinking.

 

All the "Pro" versions did was reduce ampglow, then AP'ers upped the exposure times to reinstate amp glow. Then complained. Presently seem 2 ZWO's that say "No amp glow" and appear to deliver. However I have little doubt that someone will manage to still achieve some. Lets face it just leave it running for an hour or two and something will go wrong and I do expect someone to try.

 

Imaging course said that something like 2 min 40 sec CMOS was equivalent to around 10+ minutes CCD. Go for 150 sec, maybe 180 sec and just get more exposures.

 

Answer seems obvious: Change thinking from CCD technology, use CMOS technology to your advantage, make use of shorter exposures being adaquate, take shorter exposures and so avoid amp glow.

 

Look at stars under long exposure CMOS images, they are all "WHITE". No color at all, all blown out. That is too long an exposure. Color in stars tends to be one of the first things I look for/at. Most have none these days.

Thank you! This makes so much sense. I will stick to shorter exposures and get more into the CMOS way of taking exposures :)



#6 aashish

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Posted 27 May 2020 - 12:05 PM

Do you have a Newt? This looks like what happens with an uncovered back mirror - and maybe the same pattern even with rotation. Have you tried with just the camera and its cover, in a dark place?

I had the camera by itself not attached to anything. It was covered.

 

Yeah, that doesn't look like any amp glow I've ever seen.  Like cuivienor said, it looks like a light leak.

Below is a shot grabbed from the web of "typical" 071 amp glow, highly stretched.  

I would investigate light leaks in your dark frame setup.

That is what I thought as well -- I did try different scenarios with lights on/off changing orientation of the camera. The same pattern was observed every time so I assumed it must be amp glow. But I will try a darker set up.
 



#7 stargzr66207

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Posted 27 May 2020 - 01:50 PM

This is a question for sg6, regarding your post. I am interested in
your quote "CMOS likely doesn't need 300 seconds".
I started out in imaging about 7 years ago, using a StarlightExpress
SXVR-H694C CCD imager. Over time, based on results, I settled on
using 360 second sub-exposures. When I obtained my first CMOS imager,
a 071, I just started using the same. Am I doing something wrong, or
would I get better results with shorter subs? What's the difference
between CCD and CMOS regarding optimum sub-exposure times. I'm looking
to learn something here. Thanks for a reply!

Ron Abbott


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