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Strange chromatic aberrations on bright stars
14 Feb, 2020 16:45
Hello all…

I am hoping someone can give me some feedback as to what may be causing some strange chromatic aberrations I see around particularly bright stars.  Here is an example image of IC434 that demonstrates the behavior.

I am using a Celestron Edge HD 8" with the 0.7 focal reducer.

Any help would be GREATLY appreciated.

14 Feb, 2020 19:10
It appears to be micro lensing artifacts. The 1600mm has this issue on bright stars as the senor does not have anti reflective coating on the sensor itself. As far as i know there is no work around other than some fancy post processing. I have the same camera and i unfortunately just try to avoid really bright stars.

14 Feb, 2020 23:50
Yep, Dan is right.   Those "aberrations" are the result of the Panasonic MN34230ALJ sensor.  It is a microlens diffraction pattern.  If you search for "microlens diffraction 1600", you will find a lot of posts but no solutions.  It is the only major downside of this camera.     I try to remove them through clonestamping but it is a tedious process.  The problem is a bit more manageable with less exposure time.

The astrophotography market is just not big enough to ask Panasonic to respond to this.  Some other cameras, such as the ZWO ASI183, use different sensors and do not have this issue, but have other limitations.  As with most things in this hobby, it is all about tradeoffs.
15 Feb, 2020 01:09
Hi Gary, Dan,

Can the microlenses on the sensor produce this even when the star itself doesn’t fall on the sensor?
15 Feb, 2020 02:22
Thank you Gary and Dan for this information.  I guess I am happy to know that it's not something that I am doing incorrectly,  but it's kind of a bummer in that there is really no solution.  I guess I'll have to find a way to fix it in post.

Thanks again!

15 Feb, 2020 05:18
Your photo is awesome and super impressive.
15 Feb, 2020 06:12

In a few cases of very bright stars, I have seen reflection problems when the star doesn't fall on the sensor.  But I believe that is a different issue as I haven't been able to reproduce it easily, and when it happens to me it is typically just a bright glow, and not the exact same pattern that you see in the Tim's image.

15 Feb, 2020 10:56  in can see in my photo the same problem
i use zwo asi 178  , look like difrraction
15 Feb, 2020 12:41
Hi Gary,

Thank you for the reply. I am not familiar with that sensor, but it’s hard for me to imagine that diffraction can happen when the source of light doesn’t reach sensor at all.

On the other hand, I saw that kind (shape and color) of light quite often on SCT images taken with different sensors when there are bright stars nearby. I also have that in some of my refractor images, same shape, but much fainter. In my case, after some “detective” work, I determined that it’s internal reflection. After the suspected reflective surface is properly dealt with, I never saw it again.

So although I can’t say for sure what’s going on here, I think it will be worthwhile to investigate possible reflection inside the scope. If it is caused by sensor diffraction, then there is nothing a user can do. But if it’s internal reflection, then it’s possible to remove it.
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