Internal reflections!

[UlteriorModem]

I seem to have developed some issues with internal reflections with bright stars!

I use a UV/IR cut filter, is it al all possible it is in backwards? as in the wrong surface facing the imaging chip?

M45 Stretched by Tom Whit, on Flickr

[Star Dad]

I dunno. Does this happen with other stars? I presume you are talking about the "blue" circles? I've not encountered that problem before. Might it be dust particles? Not sure how you could put a filter on backwards - all of mine are threaded to go on only one way... threads toward the camera. Mine are 2", though and have a rim for your hands to grasp the filter and the threads are "behind" that... so the grip is slightly bigger than the threads. If this helps? :

[UlteriorModem]

It is or was a 'loose' unmounted filter for a filter wheel. I put it in a filter ring for my current assembly. It is a 2-inch ZWO UV/IR cut filter btw.

Yes the blue circles above and to the left of the bright stars. Its not 'dust' as my flats prove.

I noticed this first with my recent M42 image and this morning went to process the M45 data and there they are more prominent. Of course, M45 is kind of an 'extreme' example.

Been researching to try to figure out what is actually the 'proper' orientation for it. Maybe by looking at reflections or color somehow.

[DEnc]

From https://www.baader-planetarium.com/en/b ... telescope/

"Always put the more reflective side towards the telescope side....But this is true only for instruments without optical elements near to the focal plane. If you have a coma corrector, field flattener, focal reducer, focal extender...a few centimeters in front of the filter it could be useful to flip the filter....If in doubt, it helps to make some test images from a star field with bright stars, using the filter in both ways for comparison."

[UlteriorModem]

Yea I guess the only 'real' way to test it is to flip it over and see.

Dont think my filter has the arrow on it. But will take a closer look.

Kind of a pita tough.

Thanks!