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Imaging problem with C8 & ASI120MC camera


TasKiNG

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I have been using my ASI120MC camera to video jupiter and noticed a couple of marks in the centre of the image.


I cleaned the filter and the sensor thinking it was dust but it made no difference. 


With the wide angle lens that came with the camera fitted, the marks are not there.


I then noticed that the marks look like a small image of my corrector plate with the secondary mirror in the middle.


 


I assume that it is an internal reflection off the ASI120MC's filter.


 


Has anyone else seen this problem?


Any ideas on how to fix it without removing the protective filter on the ASI120MC?


 


My telescope is a Celestron C8 and I am using a X-cell 3x Barlow.


 


asi120mc_reflect.jpg


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I use the same scope with the zwo 120mm camera, no problem like yours, I would also say dust bunnies but they could be anywhere along the imaging train

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I use the same scope with the zwo 120mm camera, no problem like yours, I would also say dust bunnies but they could be anywhere along the imaging train

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I use the same scope with the zwo 120mm camera, no problem like yours, I would also say dust bunnies but they could be anywhere along the imaging train

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Thanks Steve,


 


Just done some more testing and the spots stay in the same place when I rotate the camera.


However if I loosen it off and wobble it around then the dots do move slightly which would rule out sensor dust.


If I remove the 3X Barlow then there are no dots at all.


 


Here's my setup:-


imager.jpg


 


Here's what I see with the Barlow fitted but no camera. I think this is being reflected on the cameras IR filter:-


just_barlow.jpg


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if it stays still when you rotate cam its on the cam

 

It moves if I wobble the cam around so can't be the camera. 

Also I just tried blocking off half of the front of the telescope and the marks turn to semi-circles.  Mad eh? :)

 

I have processed the image and have brought out a number of fainter ones too:-

stacked_reflections.jpg

 

Here's a snapshot with the barlow removed. Shows no evidence of dust.

no_barlow.jpg

Edited by TasKiNG
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Problem solved. 


I loosened off the front of the camera so I could rotate the IR filter and the spots move around with the filter, not the CCD.


Explains why they moved when the camera was wobbled as the shadow cast onto the ccd would move.


Cleaning both sides of the IR filter made no difference so have removed it.


Nice clear image now :)


 


Thanks Steve/Rob for your help


Edited by TasKiNG
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Glad you found it. I had similar once I tried cleaning everything in the chain. It was maddening and turned out to be a UHC filter I was using no amount of cleaning would remove the smudge so the last I saw of that filter was flying through the air towards the bin

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Guest AstroOlly
Thanks Steve,

 

Just done some more testing and the spots stay in the same place when I rotate the camera.

However if I loosen it off and wobble it around then the dots do move slightly which would rule out sensor dust.

If I remove the 3X Barlow then there are no dots at all.

 

Here's my setup:-

imager.jpg

 

Here's what I see with the Barlow fitted but no camera. I think this is being reflected on the cameras IR filter:-

just_barlow.jpg

On a different note, the camera is a long way from the Barlow in that picture, it must be working at about 5x you will do well to get a sharp image at that distance, or is it an Celestron equivalent powermate? In which case the magnification won't increase much.

I would put the Barlow on the other side of the flip mirror before the camera.

Just my opinion

Olly

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