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ampglow showing on my 8" SCT integrations

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16 replies to this topic

#1 Ballyhoo

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Posted 22 August 2019 - 04:00 PM

I have to attribute this to the flats, no?  I am not having calibration issues with my other telescopes but in the case of the SCT, only thing I can think, and i am not sure whether this is or is not a problem, the light-panel (you know that $28 one from Amazon) is not quite wide enough on two sides of the of the OTA so that the light distribution at least on that limited portion is not even.  But would that account for amp-glow?

 

camera used was the ASI1600 OSC and the mean saturation value of the flat was 22000. 

 

Thank you!

Attached Thumbnails

  • ampglow bubble sct.png
  • flat.jpg


#2 OldManSky

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Posted 22 August 2019 - 04:15 PM

Amp glow *should* be completely gone after dark processing.  If it's still in the light frames after dark subtraction, your darks aren't matching your lights.

If it's still in flats after dark processing, your dark-flats aren't matching your flats.

 

So while it could indirectly get into your images through flats, it's always always always a dark-frame issue. :)


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#3 f300v10

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Posted 22 August 2019 - 04:15 PM

Amp glow is more often associated with much longer exposures than you should be using to take flats.  Did your calibration include dark frames of matching gain, exposure time and temperature?  Darks will usually remove most if not all amp glow from a calibrated image.



#4 Ballyhoo

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Posted 22 August 2019 - 04:37 PM

thanks I didn't think about the darks. I am going to recheck all those variables.  So perhaps my flats were fine. Do you think I need to get a larger panel for that OTA? it's about 1/4" narrow on two sides for that 8" OTA.



#5 Jim Waters

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Posted 22 August 2019 - 05:03 PM

Looks like an internal reflection and/or bright star at the very edge of the optics.  Calibrate without Flats and see what happens.


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#6 Ballyhoo

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Posted 22 August 2019 - 05:04 PM

Amp glow is more often associated with much longer exposures than you should be using to take flats.  Did your calibration include dark frames of matching gain, exposure time and temperature?  Darks will usually remove most if not all amp glow from a calibrated image.

everything matched except the darks were at -10C and the subs were at -12.7 C.  I set my Tec at -12C.  Maybe I should create a new dark library to match, bit this is not been an issue until I used the C8 (Meade).



#7 Ballyhoo

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Posted 22 August 2019 - 05:09 PM

for example there is no ampglow here and i just checked, the subs were tec at -12C and the darks were done w tec indoors, only went down to -19C

 

So maybe if there is a mismatch, it needs to be on the side of the darks being colder. 

 

https://www.astrobin...421738/?nc=user


Edited by Ballyhoo, 22 August 2019 - 05:10 PM.


#8 OldManSky

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Posted 22 August 2019 - 06:27 PM

everything matched except the darks were at -10C and the subs were at -12.7 C.  I set my Tec at -12C.  Maybe I should create a new dark library to match, bit this is not been an issue until I used the C8 (Meade).

1 degree C difference will probably not be noticeable.  2.7 C...probably will.  

They match in exposure time and offset otherwise, right? :)



#9 Ballyhoo

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Posted 22 August 2019 - 07:29 PM

1 degree C difference will probably not be noticeable.  2.7 C...probably will.  

They match in exposure time and offset otherwise, right? smile.gif

for sure...



#10 Monkeybird747

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Posted 22 August 2019 - 08:02 PM

I thought we went over this 4.gif. Shoot some darks at the matching temp. Stop trying to calibrate frames at different setpoint temps with this camera. It's so easy to do properly with setpoint cameras. I don't understand why you would even have mismatching temps? BeatingADeadHorse.gif

 

If the lights are at - 12C, shoot some -12 dark and bias frames and call it good.

 

Reshoot the darks at the proper temp. If your flats don't match reshoot those too unless the camera has been moved around. If you still have amp glow calibration issues after that, post up your data and we will find the cause.

 

If you want to try something in the mean time, check the CMOS-forbidden box in PI labeled "optimize" under your darks and recalibrate. Maybe the darks will scale good enough to get rid of the glow.

 

Its not your flats, your scope, or your light panel.

 

flowerred.gif


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#11 Monkeybird747

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Posted 22 August 2019 - 08:05 PM


for example there is no ampglow here and i just checked, the subs were tec at -12C and the darks were done w tec indoors, only went down to -19C

 

So maybe if there is a mismatch, it needs to be on the side of the darks being colder. 

 

https://www.astrobin...421738/?nc=user

 So which frames in the stack were -19c?

 

By the way, the bubble looks cool. Nice job. Now go grab another 5 or 10 hours on the same target and stack it all up.


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#12 Monkeybird747

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Posted 22 August 2019 - 08:10 PM

 So which frames in the stack were -19c?

 

By the way, the bubble looks cool. Nice job. Now go grab another 5 or 10 hours on the same target and stack it all up.

I think I understand. You were referring to a different bubble image shot at some other time?

 

2 degrees probably isn't going to make a huge difference, but still its good practice to match everything up temp wise and set yourself up for success in post processing. That way when something like this happens you don't have to wonder if its the fact that your temps don't match causing the problem. One less thing, and all that.

 

Can you screen shot your calibration settings?



#13 gezak22

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Posted 22 August 2019 - 09:24 PM

Have you tried this? I recommended it in your previous thread about amp glow.


Edited by gezak22, 22 August 2019 - 09:25 PM.


#14 Ballyhoo

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Posted 23 August 2019 - 12:01 AM

Have you tried this? I recommended it in your previous thread about amp glow.

It is not often anymore that I have this amp-glow issue, but since I had it with the different scope, I was also wondering whether different instruments have different tolerances for how calibration is done.  In the specific case it was w BPP, so all the calibration frames were mixed in the blender at the beginning. It makes sense though about the dark frame temp's. Yes all the gain and sub times are equivalent but there are variants in the dark frame library temps which were done indoors versus outdoors where I am setting the tec at -13C. But the dark frame libraries were not done with my same tec settings. Hasn't been a problem except with that one instrument.  So I was also wondering about that ligh panel fitting on well. 

 

Thank you !



#15 RazvanUnderStars

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Posted 23 August 2019 - 08:01 AM

This page by ZWO may be of help as well: https://astronomy-im...-amp-glow.html 



#16 kyle528

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Posted 23 August 2019 - 10:55 AM

*sigh* Did you already forget the post you made about amp glow just a couple weeks ago? It was explained pretty well there.

https://www.cloudyni...-in-this-image/

Follow the advice given to you in this thread. If you still are having problems, that’s the time to ask a question.


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#17 Ballyhoo

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Posted 23 August 2019 - 11:25 AM

*sigh* Did you already forget the post you made about amp glow just a couple weeks ago? It was explained pretty well there.

https://www.cloudyni...-in-this-image/

Follow the advice given to you in this thread. If you still are having problems, that’s the time to ask a question.


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No I did not forget, but again, I thought I conquered the issue and then the amp-glow popped up in the one integration. It is just reminding  me how this hobby requires meticulous operation. 

 

Okay I am once again going to review the thread, and what another member went over with me on Teamviewer. I am sure the answer is there.

 

Thank you !!


Edited by Ballyhoo, 23 August 2019 - 11:26 AM.

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