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Can someone explain what is causing this pattern around bright stars

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#1 dwertz

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Posted 24 June 2022 - 02:13 AM

Can someone explain what is causing this pattern around bright stars?  I am thinking it must be from the camera.  Possibly reflections between the sensor and the window in front of the sensor?  I can't think of anything in the scope that would cause this.

 

I am trying to decide on a 90 to 100 ish refractor and have been considering the Espirit 100ED.  There is a used one for sale, and there is a link to images taken with the scope.  I am not a fan of this pattern.  The following image is a stellarview SVX130T and does not show the pattern.  I am wondering if this is a feature of the scope, or the camera, or possibly an interaction between the two.

 

Thanks for any insights.

 

Dan

 

Espirit.jpg

 

 

 

Stellarview.jpg



#2 pyrasanth

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Posted 24 June 2022 - 02:44 AM

The pattern you are seeing is caused by the pixels on your camera creating a reflection as each pixel has a tiny lens. It is a common issue for some classes of camera and is not correctable as it is inherent in the sensor makeup.

 

This is called micro-lensing and is seen worse on brighter stars. I'm not sure if there is any post processing mitigation that can be performed.


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#3 Tapio

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Posted 24 June 2022 - 04:13 AM

What pyrasanth wrote. ASI1600 is notorious example of having it.

Don't know either an easy and effective fix for it.



#4 dwertz

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Posted 24 June 2022 - 01:28 PM

Thank you for the explanation.  The first image was indeed captured with the ASI1600MM Pro.  The second image was captured with the QHY600C.

To be clear, none of the image samples are mine.  They are both from Astrobin.

I am considering the QHY268M as my imaging camera.  From reading the linked threads, it looks like two effects, microlensing and some reflection effect from the filters.  It appears the Astrodon filters are better in that regard.  Good to know it is not the scope itself.



#5 ChrisWhite

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Posted 24 June 2022 - 02:18 PM

The pattern you are seeing is caused by the pixels on your camera creating a reflection as each pixel has a tiny lens. It is a common issue for some classes of camera and is not correctable as it is inherent in the sensor makeup.

 

This is called micro-lensing and is seen worse on brighter stars. I'm not sure if there is any post processing mitigation that can be performed.

It's not microlensing.  Microlensing is a form of gravitational lensing caused on the galactic scale.  

 

What is seen in the image is a microlens diffraction pattern. 

 

Sorry... pet peeve of mine every time I see this labeled as microlensing...


Edited by ChrisWhite, 24 June 2022 - 02:18 PM.

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#6 don314

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Posted 25 June 2022 - 10:31 AM

Read this:

 https://www.cloudyni...d/#entry8877448

 

The explanation at the start of the post is wrong, as you read through the post the explanation changes. 


Edited by don314, 25 June 2022 - 10:34 AM.


#7 Borodog

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Posted 25 June 2022 - 11:41 AM

This may be addressable via camera rotation between frames, like rotational dithering. You would need an ASCOM camera rotator and to set up your sequence to rotate between frames.


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