Is this microlense interference?

[MarkInSpace (Mark)]

what could cause this interference pattern ? This is a stacked RGB image taken using a 650mm refractor and an ASI2600MM. Most of the interference ssems to be coming from the green image.

[oska (John)]

I'm not sure what that is, but very interested.
Micro-lens I thought presented as a checkerboard type effect? Pretty sure there are threads here and on CN/SL showing it.

[MarkInSpace (Mark)]

Hi John!
Micro-lens I thought presented as a checkerboard type effect?
Thats what I thought too - could it be from the anti dew strip?

[The_bluester (Paul)]

Microlensing does not seem to be an issue with the 2600 series, the ASI1600 suffered from it and it looked like this image (On bright stars)

What you have there looks more like stacking artefacts or hot pixels.

[ronson]

Hi Mark,
I've seen the same 'effect' with ZWO OSC and Mono cameras with different filters. It only happens on very bright stars and is not consistent, i.e., might be there one night and then might be gone for a while.

I haven't been able to find the root cause, but from testing with different parts of the imaging train, I suspect it is caused by a combo of the filter and/or the camera protection window.

If you try and rotate the filter or turn it around, or rotate the camera, then the effect might be reduced or be gone.

There are discussions on CN with people reporting similar 'effects', but I don't think anyone has gone to the bottom of it.

[The_bluester (Paul)]

Actually for clarity, are you talking about the ocasional little spots (Red arrows) or the "Hairy" bright star? (Green arrow)

If the red, it might be hot pixels or stacking artefacts, if the green it may well be the limits of the scope itself. I don't have the same target with both scopes, but the first (Christmas tree) was shot with a borrowed Stellarvue SV70T and my ASI294MC Pro camera, the second image with my own Stellarvue SVX80T scope and the ASI294. The bright stars are noticeably nicer using the SV80T, the big difference between the two was semi off the shelf optics in the 70 (But still really nice) and bespoke, hand fine figured optics in the SVX80 (Which cost nearly twice what the SV70 did)

It is a bit of a giggle looking back that far, getting the colour right always seemed to be a challenge with the ASI294 MC. Much easier with the current cameras, a pigeon pair of ASI 2600MM and MC, I just wish the MM was out when I bought the first one or I would have two of those.

Christmas tree
https://www.astrobin.com/full/hcyo4r/0/

NGC5367
https://www.astrobin.com/full/1bouo7/0/

[MarkInSpace (Mark)]

Hi!
I was referring to the “gappy star” green arrow. The problem seems to be intermittent and more noticeable on bright stars.
It reminds me of newton rings that I used to get when scanning close flat surfaces.

[oska (John)]

Originally Posted by MarkInSpace

Hi John!
Micro-lens I thought presented as a checkerboard type effect?
Thats what I thought too - could it be from the anti dew strip?

I don't think it's dew heater heat, that looks more like unusual longer spikes.
This is from 2600mc, same problem (really obvious in pic2) https://www.iceinspace.com.au/forum/...d.php?t=203421

I suspect, like you, it's a very bright object problem

[The_bluester (Paul)]

The only time I have seen something like that that came and went it appeared to be seeing related on my Newtonian (Longer focal length so probably more sensitive to it) and it improved with higher altitude of the target.