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Anyone else with this Halo issue? (AT10RCT/STL-11000)

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#1 Complexmystery

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Posted 21 January 2021 - 01:41 PM

My first guess was based on a previous thread nearly a year ago about the primary baffle tube in these scopes not being long enough. After 3D printing an extension, the halo was still present on test flats. I would also suspect internal reflections, although, everything in my system is pretty dark. Train: Moonlight 2.5" focuser->RCFLAT3->Celestron OAG->STL. The connections for the OAG are from PreciseParts and are much larger than M48 (which even so would only exhibit vignetting). Maybe it is a filter issue? At this point I have no clue. Any suggestions would be appreciated. Perhaps my extension tube was still not long enough for the primary baffle. Anyways, clear skies!

 

-Josh 

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#2 Rasfahan

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Posted 21 January 2021 - 01:44 PM

I have the same kind of halo in all my O3 frames, no matter the scope, for me it is certainly a filter issue.



#3 happylimpet

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Posted 21 January 2021 - 01:45 PM

I cant say for sure but I would strongly suggest removing the camera only and moving your eye across the focal plane with the scope pointed at the daytime sky, lookng for any reflections/scattered light from internal baffles etc. Sure youll spot something.


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#4 Complexmystery

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Posted 21 January 2021 - 02:20 PM

I cant say for sure but I would strongly suggest removing the camera only and moving your eye across the focal plane with the scope pointed at the daytime sky, lookng for any reflections/scattered light from internal baffles etc. Sure youll spot something.

Thanks for the suggestion, I’ll have to give it a shot. 
 

-Josh 



#5 matthisk

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Posted 21 January 2021 - 03:29 PM

I had the same effect in Ha and O3 on my FSQ + ASI6200 with Chroma Filters and also Baader. Replaced them with Astrodons and all fine then.


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#6 Ethanwyh

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Posted 22 January 2021 - 04:52 AM

This seems to be an internal reflection stemming from the sensor's window and filters. This usually arises when the distance between the sensor window and filters are too close. One solution would be to increase the distance between the filters and sensor window via installing spacers in  bewtween.


had such issues on a newtonian and 3.5nm filters. My sensor window was AR coated and that probably played a part in this issue. 

Check this article out: https://www.baader-p...gest_causes.pdf

 


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#7 Roberto Marinoni

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Posted 22 January 2021 - 05:07 PM

I had similar issue with my GSO RC12 + TSRCFLAT3 + Moravian G3-16200 with its specific OAG + Baader filters.

The issue was very well visible on flat frames but nevertheless I was not able to remove from my light frame.

I removed the TSRCFLAT3 from my optical train and the issue disappeared (keeping same camera and filters).

I suggest you to try to remove the corrector and see if the issue is still present.


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#8 Complexmystery

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Posted 22 January 2021 - 10:24 PM

This is an old image using my previous setup. Obviously things like focus were off but that's besides the point. As you can see the light is mostly even across the field until it starts to fall off-axis which is to be expected. 

Different STL-11000 (Custom Scientific)

3" Optec Focuser

RCFLAT3

No OAG

 

 

Current setup 

STL-11000 (Baader filters) Different

Celestron OAG (with large precise parts adapters so vignetting won't be an issue) Different

RCFLAT3 Same

2.5" Moonlight focuser Different

 

So I did some thinking. I had this issue back when using the 2" flattener because of a reflective spacer. There MUST be internal reflections from something Focuser->CCD if the above image doesn't show the same effect using the same scope. So that takes away the primary baffle question. I think my best bet is to look in daylight for a reflective surface as mentioned above. That should rule out if it is a shiny adapter/oag or if it is the result of reflections between the sensor/filters. I will keep you guys updated. I should be able to do some testing tomorrow. Thanks for the recommendations guys. I would like to mention that the center "halo" in the first image is a mere 500-1000 counts higher than the center of the image. It may be that something is just slightly reflective. 

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Edited by Complexmystery, 22 January 2021 - 11:10 PM.


#9 Complexmystery

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Posted 22 January 2021 - 10:36 PM

Sorry for the bad quality due to file limits. Here is a quick contour plot of the old image vs the new one. Something is obviously not right haha. 

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#10 Ethanwyh

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Posted 24 January 2021 - 09:35 PM

How close are your filters to your sensor window? I found this issue quite prominent in my Oiii sub. 
Also, did reversing the filter help?

 



#11 Complexmystery

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Posted 24 January 2021 - 10:16 PM

How close are your filters to your sensor window? I found this issue quite prominent in my Oiii sub. 
Also, did reversing the filter help?

Removed filters and problem still existed. I saw a reflection off of what I thought was the flattener. It's actually coming from right in front of the flattener.....the focuser. This explains why the issue did not show up on my previous system (Optec TCF-S). So, now to figure out what I want to do to make the surface non reflective. I will need to take a test shot to confirm, but I am 99% certain this is the issue. I'll update with some images once I have them. 


Edited by Complexmystery, 24 January 2021 - 10:17 PM.


#12 Complexmystery

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Posted 25 January 2021 - 12:41 AM

Well, final verdict. Reflection coming from the end of the Moonlight focuser. I covered it with some stick on Velcro that I had lying around. Seems to have worked like a charm. Glad to finally have this sorted out. 

 

Thanks everyone for the suggestions!

-Josh 

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#13 happylimpet

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Posted 25 January 2021 - 05:42 PM

Cool! I thought so.

 

And velcro as a flocking thing!!! Bloody brilliant! Thanks for that idea.


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#14 Complexmystery

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Posted 25 January 2021 - 07:04 PM

Cool! I thought so.

 

And velcro as a flocking thing!!! Bloody brilliant! Thanks for that idea.

Your idea of looking during the day definitely helped. Of course I looked multiple times when trying to do indoor flats. But, it wasn't quite bright enough. During the day the reflection stood out like a sore thumb. As for the Velcro, I'll see how it goes in terms of staying on there. As for it's ant reflectivity it seems to do extremely well. 


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