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Amp glow not fully calibrating out  

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(@seeker372011)
White Dwarf Customer
Joined: 5 months ago
Posts: 11
September 12, 2021 23:03  

Hi

 

i am a fairly recent APP user so forgive me if I am asking a newbie question.

 

I have been working on a target with data collected last year as well as data collected this year- a total of 24 hours, mostly 10 minute subs; I shoot darks every single time ( I don’t use a library) to make sure I use the same gain and offset and always at -10 degree C. I also shoot Flats after every session to take care of any minor variations in rotation. I use a CMOS - a QHY183MM where the amp glow is fierce. All images in this instance are in H alpha 

 

This is my problem- while on inspection in APP the calibrated frames don’t show any amp glow, when I take the stretched image to Photoshop for further stretching amp glow reappears very noticeably 

Using LNC -level 1, one iteration helps a lot but doesn’t kill it. LNC level 1 3 iterations made little difference.

I have tried same camera and optics both ticked and un ticked- not sure why that would be relevant but just in case.

any advice would be greatly appreciated, thank you

 

Thanks in advance

 

 Narayan

This topic was modified 3 months ago by Narayan Mukkavilli

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(@seeker372011)
White Dwarf Customer
Joined: 5 months ago
Posts: 11
September 13, 2021 06:55  

I should add for all sessions the adaptive pedestal option was selected in calibrating.

 

I am now trying about half the sessions - some 16 hours of data -in DSS to see if I encounter the same problem

This post was modified 3 months ago by Narayan Mukkavilli

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(@seeker372011)
White Dwarf Customer
Joined: 5 months ago
Posts: 11
September 13, 2021 07:09  

I can report the amp glow appears to be completely calibrated out in the DSS stack.

 

update- the amp glow reappeared when the stacked image was stretched really aggressively.This was the case with the APP stack as well, though it was much worse with the APP stacked image

 

any suggestions? Thanks in advance

This post was modified 3 months ago by Narayan Mukkavilli

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(@wvreeven)
Quasar Admin
Joined: 3 years ago
Posts: 1226
September 13, 2021 10:53  

@seeker372011 Hi Narayan. It sounds to me as if the darks have not been taken properly. There are some sensors that are notorious when it comes to amp glow, making it very hard to remove it. Let me know if you would like me to have a look at your data to see if I can give you some tips. We have a server where you can upload the data so there is no need for you to upload them to a cloud storage of your own.


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(@seeker372011)
White Dwarf Customer
Joined: 5 months ago
Posts: 11
September 13, 2021 12:08  

Yes please it would be great if you could have a look.

 

as I said DSS is removing far more of the amp glow than APP- so I am not entirely sure the problem is with the darks. The DSS result is almost - but not quite - perfect

 

Shall I upload a few lights and a few darks  - maybe one from each session?


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(@wvreeven)
Quasar Admin
Joined: 3 years ago
Posts: 1226
September 13, 2021 12:43  

@seeker372011 I would need a few of lights, darks, flats and either bias or dark flats (or both) depending on what you use. You can upload to

https://upload.astropixelprocessor.com/

with username and password: upload

Create a folder called seeker372011_amp_glow and put the files in there. Let me know when the upload is done by using the reply link under this message so I receive an email when you reply and I will have a look asap. Thanks!


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(@seeker372011)
White Dwarf Customer
Joined: 5 months ago
Posts: 11
September 14, 2021 03:50  

@wvreeven, I just uploaded  a few lights, darks, flats and dark flats to a folder named as you suggested.

 

I also uploaded a stretched image which shows the remnant “starburst” amp glow on the right hand side, which is the problem I am struggling with.

 

thanks so much for offering to assist, I really appreciate it

This post was modified 3 months ago by Narayan Mukkavilli

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(@wvreeven)
Quasar Admin
Joined: 3 years ago
Posts: 1226
September 14, 2021 11:24  

@seeker372011 I first integrated the session 1 lights and I think that I may have seen a little amp glow on the right border. It is hard to tell with only three lights. Then I integrated the session 4 lights and I saw no amp glow at all but I did see a satellite trail. Then I integrated all lights together and I think that the amp glow may have returned again. Once again, only a few files so it is hard to see if it is there at all. Here is a screen shot of the last integration:

Screenshot 2021 09 14 at 11.17.44

How do you integrate all sessions? Do you create integrations per session and then integrate those together again? Or do you load all data into individual sessions and integrate them all into one result? Or do you load all data into one session and integrate?


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(@seeker372011)
White Dwarf Customer
Joined: 5 months ago
Posts: 11
September 14, 2021 13:23  

@wvreeven in this case I loaded all the lights, darks, flats and flat darks each as a session- so nine sessions. One calibration and integration.

 

would it make sense to integrate each session separately and then register and integrate all the sessions?


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(@seeker372011)
White Dwarf Customer
Joined: 5 months ago
Posts: 11
September 14, 2021 13:26  

@wvreeven ps yes that is most definitely the amp glow - the starburst..gets worse when all 196 odd frames are stacked


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(@seeker372011)
White Dwarf Customer
Joined: 5 months ago
Posts: 11
September 14, 2021 13:26  

@wvreeven ps yes that is most definitely the amp glow - the starburst..gets worse when all 196 odd frames are stacked


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(@wvreeven)
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Joined: 3 years ago
Posts: 1226
September 14, 2021 13:42  

@seeker372011 I don’t think that integrating them separately will make a difference. Do you see the amp glow in each of the nine session integration results?


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(@seeker372011)
White Dwarf Customer
Joined: 5 months ago
Posts: 11
September 14, 2021 22:19  

@wvreeven thanks for the response. I haven’t tried integrating sessions separately- but will try a few sessions chosen at random and see if it is in all or only some and report back

 

thanks for your support 


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(@seeker372011)
White Dwarf Customer
Joined: 5 months ago
Posts: 11
September 15, 2021 05:22  

@wvreeven I just checked a few individual sessions by stacking them separately 

 

I found the amp glow in all but a lot less in last years sessions compared to this years. The difference was in the spacers I used- this years is supposed to be optimised to manufacturer recommended 55mm last years was a bit off

 

I also checked data collected with another CMOS camera- same chip but colour - on the same object taken this year and using the same telescope etc…and found amp glow.

 

went back and checked data collected with the same camera but another telescope - a REdCat instead of an ED 80- and found zero amp glow 

 

so it appears Prima faci the problem is with this particular imaging train…for some reason with same gain offset and exposure duration the amp glow is calibrating out in one imaging system- the RedCat - but very poorly in the other.

 

the only other difference was in the duration of the flats- with the RedCat I used 1.71 seconds with the ED80 I used 2.7 seconds, ( using the Flat Wizard in NINA) 

 

this is getting weirder and weirder 

 

I am getting a new flattener for the ED80 today as my current reducer/ flattener is not giving me a flat field to the edges, Could this help? Who knows but I will try and see what results- and report back in case it is of interest or help to anyone else

Any suggestions advice will be most gratefully appreciated 

Dont know when I will next get clear skies of course!


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(@wvreeven)
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Joined: 3 years ago
Posts: 1226
September 15, 2021 10:39  

@seeker372011 I would be very surprised if the reason for residual amp glow were the flats. As a matter of fact, I redid the integration with your session 1 files and this time NOT using flats and I still see the hint of amp glow in the result. So I am pretty sure that the flats are not the cause.

Have you tried integrating the RedCat files once more with the APP version that you use for processing your Helix Nebula pictures? If you did, do you still see no amp glow in the result? That could be a good check to verify that the likely cause is in the imaging train.


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(@seeker372011)
White Dwarf Customer
Joined: 5 months ago
Posts: 11
September 15, 2021 10:48  

@wvreeven

 

yes I did exactly that

 

i pulled out old data- August 2021 - and used the identical AAP settings on both the old data from my other telescope and on the new data

 

no amp glow in the old data, amp glow that appears in stretched images in the data from the telescope I am currently using

 

it just doesn’t make sense! But .. the problem seems to be with the current optical system

and of course the more you stack the worse the amp glow gets 🙁

 

my AstroTech flattener has arrived. Hopefully some clear nights next week when I can test

 

if that fails I will be completely bereft of ideas!


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(@wvreeven)
Quasar Admin
Joined: 3 years ago
Posts: 1226
September 15, 2021 11:07  

@seeker372011 Fingers crossed for clear skies then. And that the new flattener solves the amp glow issue!!!


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