What's wrong with my flats - Forums

Topic starter

Mar 5, 2025

Not sure why my 80 x 60s Lum stacked shot is turning out this way - RGB works good. Using WBPP in Pixinsight
Shooting in heavy LP might be a factor - is there any way to adjust flat settings in NINA for this?
Any help would be appreciated.
Thanks!

Tommi Liinalampi

Mar 5, 2025

You have dust in your luminance filter and filter wheel is not in same position when taking flats than when taking lights. Very typical result of that.

Change your filter wheel moving just one way if it's already not. Clean your filters to prevent problems if there is still some inaccuracy in filter wheel position. Hope you wont't get these creaters after that.

MeridianSkyAstronomy

Topic starter

Mar 5, 2025

Thanks - will a calibration of the filter wheel correct this?
Will I still be able to use these lights?

ZWO EAF

Tommi Liinalampi

Mar 5, 2025

I would recommend to take flats and lights in same calibration. In this case calibration would solve the problem only if it make gap between different positions shorter.

It would not be easy to fix this afterhand if this would not help. Maybe I would try to use mask around these creaters or donuts and remove some layers using MMT. But I think that you wont't get perfect result to do so.

John Hayes

Frequent contributor

Mar 5, 2025

I completely agree with Tommi but I see one other thing. Some of the dust is moving between when you take the lights and when you take the flats–and that's not good. First, clean everything–perfectly. Do the cleaning operation in a clean area. Wear a mask so that you don't get spit on your filters. And then use a duster when you are all done to get rid of any residual particles that get in. Finally, seal your system to keep the dust out. Tape up every single gap where there's an opening. In a well cleaned system, you shouldn't see more than 1 or 2 dust motes.

John

Helpful Concise

andrea tasselli

Frequent contributor

Mar 5, 2025

It can be fixed, to a signifiant degree, but it takes a bit of an effort and mastery of PI/Siril and NO WBPP. Obviously keeping everything clean beforehand is the way to go, as suggest by John and Tommi.

MeridianSkyAstronomy

Topic starter

Mar 6, 2025

I ran it again with new flats and it corrected all areas except for the biggest mote in lower right
It appears that somehow the EFW did not correctly align L filter as you said - I'm not sure what caused this as I run flats all the time but usually for narrowband
I will shoot another set of Lum lights & flats tonight & hope for a better result.
My glass will get a cleaning soon
Thanks for the input

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