Odd circular artifact in green flat

[Yawning Angel]

Hiya,

I've come across a oddity in my flats, but just for the green filter - odd circular banding. Does anyone have an idea on the source - to me it looks like tube baffling? FITS linked below, with the Luminance flat for comparison

ZWO asi1600mm-pro / Sky-watcher ED80 and reducer. ZWO Filter wheel and matched filters

Flats taken with an illuminated panel and several sheets of heavyweight paper

MF-Green.fits

MF-Lum.fits

Thanks for looking!

[ollypenrice]

That's odd. Does a hyper-stretch of the green data show any sign of similar artefacts? 

If not I would just use your luminance flat for green. To be quite honest, most of the time I find no need for 'flats per filter' and get just the same result when using a luminance flat for them all. Very occasionally this doesn't work but my bunnies are clearly not often caused by dust on the filters.

It could be that your green filter sets up internal reflections for some reason. I guess the ZWO filters are interferometiric rather than absorption?

Olly

[Yawning Angel]

Olly,

Thank you. I've had a look at some of the green subs, and the artefact doesn't show up - I'll re-run using just the luminance flats, and see how it looks.

With regards the filters, I don't know which type the ZWO ones are...and my google-fu has failed to tell me. I'll post my results ?