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RC12 telescope produces astrophotos with parasite lights

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#1 jbenito

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Posted 09 December 2023 - 01:41 PM

Hi everyone. I recently bought an RC12F8 telescope (second hand) made by CFF telescopes from Poland. After sometime fine tunig the system (RC12F8 plus ASI2400 CMOS full frame camera) I realized that most of the pictures taken so far are polluted with parasite arcs of light, sometimes all around the frame. 

I contacted Catalin from CFF telescopes and he told me most likely the problem was due to a short baffle of the secondary mirror (M2 miror). So he dent me an extender for the M2 baffle. I have the orotunity to test the M2 extender this weekend to check if this fixed the problem. However it did not (not completely). I attach a word document containing screeenshots of the images I took without and with the M2 extender).

 

Your opinion (and experience in case some oy you out there has had this same problem with this brand of RC telescope)  is very wellcome

 

Thanks

Jose M Benirto



#2 pfile

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Posted 09 December 2023 - 02:10 PM

interesting - some celestron 6 SCTs exhibit these weird arcs as well, but without seeing an image from your telescope it's hard to know if it is the same. in the case of the 6" SCT, the problem is a shiny primary mirror baffle. you might check both baffles on your telescope to see that they are flocked properly.


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#3 jbenito

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Posted 09 December 2023 - 05:17 PM

Thank you for the feedback. In my first post I included a Word file with images taken with th RC12

#4 sharkmelley

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Posted 09 December 2023 - 05:24 PM

It's impossible to comment without seeing an image of what the problem is.  There's no Word file attached to your post.



#5 jbenito

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Posted 10 December 2023 - 05:28 AM

Sorry. I attach the word file again

Attached Files



#6 sharkmelley

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Posted 10 December 2023 - 06:56 AM

What you are seeing is a common problem which is discussed in these threads and many others:

https://www.cloudyni...my-reflections/

https://www.cloudyni...age/?p=10045010

 

The light from a star outside the field-of-view is reflecting off the curved internal surface of an adapter, baffle, focuser or some other part of the optical train.  You need to find that reflective surface and either flock it or spray it with matt flat paint.


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#7 jbenito

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Posted 10 December 2023 - 08:27 AM

Thanks so much for the two links comenting on this issue. The two cases comented on the links are with refracting telescopes. So I guess this can also happen (with the same underlying mechanism) with an RC telescope, is this right?. If this is the mechanism, then the solution I was thinking of (extending the primary mirror baffle) does not aplly, right?. I should look for all the adapters between the rear end of the RC and the camera sensor, to check if all the surfaces are matt black. I use a lens for field correction. I took the same photograph with and without this lens and I got the arcs in both cases, so I excluded the lens as the cause of the problem. 

 

Regards

Jose Miguel



#8 sharkmelley

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Posted 10 December 2023 - 01:12 PM

The two cases comented on the links are with refracting telescopes. So I guess this can also happen (with the same underlying mechanism) with an RC telescope, is this right?. If this is the mechanism, then the solution I was thinking of (extending the primary mirror baffle) does not aplly, right?

That's right.  The same mechanism happens with all types of telescope and it cannot be prevented by extending the primary mirror baffle.



#9 Dan Crowson

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Posted 10 December 2023 - 03:45 PM

I can't see the issue in the word document images because of the size but if you're getting arcs, it is typically light getting around the baffle as mentioned. You mentioned an extension but still having the issue. You can test the theory but rolling up a piece of black paper or felt sheet (found in a craft store) or something similar and just stick it into the baffle and take some images. I found this to be the issue with my AT12RCT (first generation) before there were a lot of threads mentioning the issue and 3d printing baffle extensions to fix it.

 

Here's an example of the issue with mine - AT12RCT%20Primary%20Baffle%20Tube%20Issu



#10 sharkmelley

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Posted 10 December 2023 - 04:47 PM

I can't see the issue in the word document images because of the size but if you're getting arcs, it is typically light getting around the baffle as mentioned. You mentioned an extension but still having the issue. You can test the theory but rolling up a piece of black paper or felt sheet (found in a craft store) or something similar and just stick it into the baffle and take some images. I found this to be the issue with my AT12RCT (first generation) before there were a lot of threads mentioning the issue and 3d printing baffle extensions to fix it.

 

Here's an example of the issue with mine -

Interesting.  So it seems that with some RC scopes there is more than one potential cause of arcs in images.



#11 jbenito

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Posted 10 December 2023 - 05:11 PM

Thank you allí for your input.
There are two different opinions so far: one IS that the cause of the problema is light from a bright object outside of the field of view that reflecta in metal inner surfaces of adapters, etc. This can not be solved by extending the baffle tube. The other opinión isa that the cause IS light doing its way around the baffle tube. This can be fixed by extending the baffle tube.
So, I would be very Happy with the second option. I Will try extending the M1 baffle tube with cardboard to see if It works.
I have checked allí the inner surfaces of adapters/extenderse placed between the field corrector lens anda the camera sensor and allí are black anodized. Not sure if this IS enough to prevent reflections. Any idea on how yo teansform the Metallica surfaces intro something much less reflective? (Maybe gluing a piece of black Velvet on the inner surfaces of adapters/extenders?)

José Miguel

#12 andysea

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Posted 10 December 2023 - 06:02 PM

Black anodized aluminum is highly reflective. All internal surfaces should be painted with a matte black paint, or flocked. Takahashi is a good example of how to treat internal surfaces, they seem to be obsessive about that.



#13 BucketDave

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Posted 11 December 2023 - 05:48 PM

Jbenito:

As Andysea says, smooth surfaces often become very reflective when the light is near 'grazing incidence'. The solution is to make the surface very rough. Possible ways are :
1) numerous shallow baffles
2) adhesive paper covered with black 'flock'
3) black paint containing sawdust, sand etc
4) thin black leather.

I've used #3 at work and #4 at home. Both worked well.

Dave

#14 jbenito

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Posted 12 December 2023 - 07:12 AM

Thanks everyone.
This weekend I Will do two things:
.- I Will check the efecto of enlarging the primary mirror baffle using a piece of cardboard.
.- I Will paint the inner surfaces of adapters/enlargers with a matte black paint (Krylon ultra flat)

Regards
José Miguel

#15 jbenito

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Posted 17 December 2023 - 03:03 AM

Last night I did both things without any effect on the parasite reflections.
Any ideas are very appreciated
After painting the inner side of adapters/enlargers I felt that the surfaces was stil quite brilliant. Allí the adapters/enlargers are threaded in the inner side. I think that this fact makes It more difficult to eliminate reflections coming from the threads since It IS more difficult to get them completely covered with the paint. What do you think?

Thanks

#16 OmarR

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Posted 16 January 2024 - 05:20 AM

Looks like I am having a similar issue. This was taken under a bortle 1 sky in West Texas using the RCOS 16, QHY600M and Astronomik Luminance filter. The scope is completely blackened inside. Confirmed that there are no light leaks and all anodized metal has been painted with a non-reflective black paint. I have ordered baffle tube extenders with different lengths that I hope will resolve the issue.

 

M78 stretched GraXpert. BlurX NoiseX


#17 OmarR

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Posted 16 January 2024 - 05:22 AM

I should have stated that one the same night M78 was taken I slewed over to the Medusa Nebulae and was able to image the target with no issues. 



#18 Dan Crowson

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Posted 16 January 2024 - 06:32 PM

Looks like I am having a similar issue. This was taken under a bortle 1 sky in West Texas using the RCOS 16, QHY600M and Astronomik Luminance filter. The scope is completely blackened inside. Confirmed that there are no light leaks and all anodized metal has been painted with a non-reflective black paint. I have ordered baffle tube extenders with different lengths that I hope will resolve the issue.


I wouldn't spend a lot of time on this one because your issue is the bright star out of the frame that most people have issues with. This 'issue' tends to not be due to the baffles length.

Dan



#19 OmarR

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Posted 01 February 2024 - 08:19 AM

Dan,

Thank you for the info. I went ahead and added a 3" extension on the primary baffle tube and the results were immediately noticed. Here is an image I captured yesterday of the same target. This is roughly 2.5  hours of data.

 

M78 Red filter

Edited by OmarR, 01 February 2024 - 08:20 AM.



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