Another Flats Issue

[PaulR1]

Hey folks

got a real problem taking flats that work

got a dimmable A3 tracing panel , place this on top of scope ( 200PDS ) Camera is a QHY168C . With a optolong L-Pro filter on it .

Flats look like this

They do nothing at all , they dont remove vignetting or fix any dust donuts. Nada lol

Any ideas ?

 

[vlaiv]

That looks fine.

Can you post single fits of flat for examination, and maybe one of each - light sub, dark sub, flat dark sub so we can see if there is issue with calibration?

[PaulR1]

Yep ,

Light

Flat  

Darkflat

Dark

added

2020-02-17_22-01-41__-15.00_180.00s_0001_10.00_70.00.fits 2020-02-18_00-43-45__-15.10_0.50s_0000_10.00_70.00.fits 2020-02-18_00-56-43__-15.00_0.50s_0000_10.00_70.00.fits 2020-01-05_11-16-03__-15.10_180.00s_0001_10.00_70.00.fits

[vlaiv]

Ok, I see no problem here what so ever.

There is slight issue that red is quite attenuated compared to other two colors - which means that your flat source produces really cool light - white bluish - possibly led flat panel?

But that can be fixed in processing by using proper color balance techniques.

Here are results of examination - first flat split into components and stretched:

Everything looks fine with this flat apart from weak red color, but that is like we said - due to light source.

Notice that there are no dust particles on the flat file - so if we find some on light that will be a problem.

Here is light without any processing:

I don't see any dust shadows on it, but I do see vignetting and that vignetting really reminds me of the flat above - stronger to the right side of the image. Let's see what calibrated sub looks like:

from what I can see here - vignetting is gone, and there is just a background gradient in this sub - going from left to right.

Once we remove that linear gradient:

That looks rather good?

[PaulR1]

Many thanks for the reply Vlaiv , appreciate your input.

I do see donuts in the image here but your right there are none on the flats and I just checked my sensor and it appears clean , so maybe the dust moved between be taking lights and flats.

Not sure

[vlaiv]

Could you show an example? Are all subs affected, or have you seen some with dust shadows and some without (maybe check - that would be a sign of dust moving).

[PaulR1]

interesting I ran through the subs and some had dust some didnt so I guess as the flats didnt have dust donuts they had nothing to remove from the stacked image which of course when stacked would have included the subs with or without the donuts.

thanks vlaiv

Edited February 21, 2020 by PaulR1