Purple brightness around stars
Purple brightness around stars
When live stacking stars, recently they have been showing this weird purple aura around the star, ive never had this happen to me before. All of the sudden it started showing up in my photos. any idea on what’s going on here? I attached a photo below! Thanks for the help.
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Re: Purple brightness around stars
Hi,
there may be two parts to this...
The fact that the glow is there could be related to something optical - is there some obstruction preventing the light getting to the sensor that is causing the glow as a diffraction pattern, or some reflections happening within the scope that could be causing this - I would check to see if anything is obstructing into the light path inside the telescope that shouldn't be there as a starting point.
The fact that it is purple hints that the bayer pattern being used for the images may be incorrect. If you zoom in on the image and see a grid/chessboard pattern at the pixel level then the bayer pattern is definitely incorrect. Out of the four bayer patterns, one will be correct, one will be incorrect and swap the red/blue channels and two will be swapping the green for the red/blue and those last two do tend to give a purple cast to images. There is some more info in the documentation, along with a sample showing how the purple might look on an image with the incorrect patter : https://docs.sharpcap.co.uk/4.1/#Debayer%20Preview
Hope this helps,
Robin
there may be two parts to this...
The fact that the glow is there could be related to something optical - is there some obstruction preventing the light getting to the sensor that is causing the glow as a diffraction pattern, or some reflections happening within the scope that could be causing this - I would check to see if anything is obstructing into the light path inside the telescope that shouldn't be there as a starting point.
The fact that it is purple hints that the bayer pattern being used for the images may be incorrect. If you zoom in on the image and see a grid/chessboard pattern at the pixel level then the bayer pattern is definitely incorrect. Out of the four bayer patterns, one will be correct, one will be incorrect and swap the red/blue channels and two will be swapping the green for the red/blue and those last two do tend to give a purple cast to images. There is some more info in the documentation, along with a sample showing how the purple might look on an image with the incorrect patter : https://docs.sharpcap.co.uk/4.1/#Debayer%20Preview
Hope this helps,
Robin
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Jean-Francois
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Re: Purple brightness around stars
Hello,
You have 2 different glows.
The first is circular (mostly centred with the star, but that depends where you place the star on the detector).
It could be the overlap of several double bounce reflection on the windows or the lenses.
You have the thin protective window on the chip itself and you have the camera window (if it is a cooling version).
In addition you can have a filter and/or a lens system (flattener or corrector/reducer).
The second glow is more interesting ... you see the reflection on the chip itself backward and reflected again by a window.
You see 8 diffraction patterns. It is fist the upper/lower/right and left direction.
In addition you have the cross effect. These are coming from the periodic pattern of the CCD or CMOS pixel.
Normally more visible with front illuminated sensor with micro-lenses.
Regards,
Jean-Francois
You have 2 different glows.
The first is circular (mostly centred with the star, but that depends where you place the star on the detector).
It could be the overlap of several double bounce reflection on the windows or the lenses.
You have the thin protective window on the chip itself and you have the camera window (if it is a cooling version).
In addition you can have a filter and/or a lens system (flattener or corrector/reducer).
The second glow is more interesting ... you see the reflection on the chip itself backward and reflected again by a window.
You see 8 diffraction patterns. It is fist the upper/lower/right and left direction.
In addition you have the cross effect. These are coming from the periodic pattern of the CCD or CMOS pixel.
Normally more visible with front illuminated sensor with micro-lenses.
Regards,
Jean-Francois