William Optics ZS61 image reflections

[Andy56]

Hi,

 

I have a WO ZS61EDII with it's flattener with the Optolong dual-band l-extreme filter and the the ASI2600MC pro.

 

I have noticed (last winter) what appear to be internal reflections by bright stars. See pics.

These appear in the Blue and Green channels but not in the red.

I've seen it on the Horse Head nebula and M42.

 

Any one any ideas what might cause this? Could be internal reflections in the filter but I thought this caused bloat.

See attached photos. I've circle the artefacts.

 

Cheers

Andy

Edited October 28, 2023 by Andy56
Spelling

[Neil_104]

Do you get these odd artefacts when not using the L-Extreme filter?

To me they almost look more like some kind of image corruption (bad bits), rather than anything physically captured. What stacking/processing software did you use? Might be worth trying out some different programs on the same data to see if the artefacts remain.

[Andy56]

I haven't tried without a filter because of light pollution.

I now have a filter tray so I can try it out when Orion rises at a better time

I used Pixinsight's WBPP.

Just re-blinked the HHN subs and it's in one session of 57 subs.  I can only see one artefact but the others could be visible after integration, possible on the other subs.

On M42 it's in a couple of sets of subs at different positions.

Wasn't looking for it originally.

So it's a genuine artefact.

I'll integrate the subs separately an see if/where it appears.

The set up was the same for each night. I think I left the set up out over the day so no changes. Can't remember exactly because it was December last year

Cheers

Andy

 

Snip from a single blue sub

Snip from a single red sub

Edited October 29, 2023 by Andy56
Annotated images

[Andy56]

So I've looked over my subs in great detail and found something very interesting.

The reflection moves around with dithering so I thought probably a streetlight (no moon) or similar on the lens. Perhaps I forgot to slide the hood up.

BUT it stays in area after a meridian flip.

I would have expected it to move to the other side of the image if it was external to the telescope.

Any one any ideas?

Cheers

Andy

[Elp]

Best thing to do is specifically image around a bright star and move the scope position around it to see if you can replicate it. Also try rotating the camera to see if it moves or not once you manage to image the abberation.

[Andy56]

Hi,

Yes good point try a bright star. Find one at the same approx alt/az position to see if it's external light source.

Cheers

Andy

 

 

[Elp]

I wouldn't rule out the external light source. When using the lextreme up front on camera lenses I noticed they didn't like stray light hitting it at angles, but the effect was much larger in area in the subs leaving green/red patterns in them covering maybe a quarter to half the image in area at times. Never seen the small aberrations you're seeing, I've got the same scope but never used this filter with it to comment.

 

[Elp]

You could also try moving the filter to somewhere else, filter drawer, screwed into the flattener etc. It could be an internal reflection issue.

[Andy56]

Hi,

The filter is in a filter draw next to the camera. I can remove the filter easily to see if it's that.

I have 3 artefacts in the final images because it appeared at different positions during different sessions.

I've created a video from one set of registered subs from the HHN. For the first 1/2 there was no dithering and about 1/2 way though it does a meridian flip and dithering starts. Then about 10 frames before the end there is scope move or something. The artefact follows the approximate location. I would have though it would have moved substantially after a flip if it was external lights and not moved if it was a bright out of view star.

One set of subs did not show it at all. This was a different night but the telescope position would have been within cms of the other occasions. My tripod goes onto 3 1/2 bricks in the lawn.

I guess I have to wait until some clear nights come back to greet us or at least some with few clouds and no rain. (and warm. Maybe move to Spain)

Cheers

Andy