Odd artifact caused by bright stars and ????

[RichardNewbie]

I have been using a new Askar 107PHQ with ASI 7nm NB filters in an ASI filter wheel in front of an ASI1600mm camera, normally running at -4'C very successfully, but have encountered a problem. Very bright stars cause an artifact, see attached, which I cannot eliminate. Is this likely to be the camera, the 'scope or something else? The artifact exists in the original fits files - it is not a processing issue. If it cannot be avoided, what is the best way to minimise/eliminate it. I have gone down to 60s exposures, but the artifact is still there (but IC63 is not). I have tried de-starring (Starnet2), healing the area using Affinity 2, then putting the stars back, but the 'healed' area always shows.

Thanks in advance for any and all help.

IC63 300s each Ha, Oiii, Sii, 0 gain, 21/1/23. HSO stacked and combined combined using APP.

[Stuart1971]

I think this issue is over the whole image, if you look here, you can see the square pattern, then there is a small gap on each side then the pattern starts to repeat, but much dimmer, as there are no more bright stars to show it up, so my guess would be a bad filter maybe…or camera window, neither have been cleaned have they and left a residue on..??

 

[Stuart1971]

Try some images with just camera and scope to eliminate the filters as being the issue

[inFINNity Deck]

This is a very clear example of micro-lensing, see https://www.cloudynights.com/topic/635937-microlens-diffraction-effect-explained/

Nicolàs

[The Lazy Astronomer]

1 hour ago, RichardNewbie said:

I have been using a new Askar 107PHQ with ASI 7nm NB filters in an ASI filter wheel in front of an ASI1600mm camera, normally running at -4'C very successfully, but have encountered a problem. Very bright stars cause an artifact, see attached, which I cannot eliminate. Is this likely to be the camera, the 'scope or something else? The artifact exists in the original fits files - it is not a processing issue. If it cannot be avoided, what is the best way to minimise/eliminate it. I have gone down to 60s exposures, but the artifact is still there (but IC63 is not). I have tried de-starring (Starnet2), healing the area using Affinity 2, then putting the stars back, but the 'healed' area always shows.

Thanks in advance for any and all help.

IC63 300s each Ha, Oiii, Sii, 0 gain, 21/1/23. HSO stacked and combined combined using APP.

The sensor used in the 1600 is well known for producing these microlensing artifacts on bright stars. Unfortunately there is nothing you can do to prevent it, other than avoid bright stars. Correction can be done in post processing, but as you've discovered, it's tricky to make it look right - practice makes perfect!

[newbie alert]

It most definitely microlensing effect from the 1600

[inFINNity Deck]

It is better to state that the effect is imaging-chip related, as the QHYCCD QHY163 and ZWO ASI1600MM (and many other models) use the same Panasonic chip from the MN34230 family. It is due to this chip and the protective window in front of it that the reflections occur.

As @The Lazy Astronomer wrote, there is nothing you can do about it, apart from using a camera with a different architecture chip (or to remove the window 🤪... no, don't do that).

Nicolàs

 

[RichardNewbie]

Thanks everybody. As for cleaning the filter etc, I had already done that but omitted to say so. Apologies. Camera micro-lensing does seem to be the issue.  At least it's not the PHQ!

[Paravision]

Thanks everyone for your thoughts. Definitely look into the micro-lensing. This is the first time I've seen this effect, so will investigate further when I get a clear night! I did use the camera with spacer ring for the first time this time. Previously I've used the camera via a diagonal. So will see if it makes a difference. You never know unless you try!

[Paravision]

Sorry, posted in wrong forum! Was related though. I was seeking advice about this image I took.

[inFINNity Deck]

Same issue here: micro-lensing. Nothing much that you can do about it apart from using a different type of camera or avoiding these bright objects. Of course you could try to select the reflections and darken them. Hopefully one day someone writes a plug-in or stand-alone program that can handle these reflections....

Nicolàs