Yet another flats question...

[Larry 1969]

I've had pretty good results using the "Flats Wizard" in N.I.N.A. You still need to create settings but it really helps dial it in.

I have been using APT's "CCD Flats Aid". I imagine it's similar to NINA. You enter your target ADU and it calculates the exposure time required.

Larry

[SkyHiker]

From the aforementioned thread https://groups.io/g/DeepSkyStacker/topi ... 3711653336 , it seems clear that my problem is caused by LP. Larry, this could be the case with yours too because stackers generally can't differentiate between obstruction-related background gradients (flats) and LP, so any LP will introduce flat-originating gradients.

[SkyHiker]

There is a setting in APP under the "Calibrate" tab for master flat integration. "Automatic" is the default. The other choices are "average", "median" and "maximum". According to the help, "automatic" will choose between "average" and "median" depending on the number of flats. Less than 20 it selects "median" and more than 20 gets "average". "Maximum" says Use maximum to show all outliers / artifacts (with too high ADU values) in the data like hot pixels, cosmic rays etc.

I restacked my image using "maximum" and it made no visible difference...

I'll keep fooling around I suppose...

Larry

But those settings only make "micro-level" changes, not the "macro-level" ones that we need to reduce the gradients that we experience, right?

[Larry 1969]

But those settings only make "micro-level" changes, not the "macro-level" ones that we need to reduce the gradients that we experience, right?

I'm sure you're right. Most of this is over my head...

Larry

[han.k]

There must be something wrong in the processes.

1) The gain used for the lights, darks, flat and flat-darks must be same.
2) Exposure time and temperature of the lights & darks should be the same
3) Exposure time and temperature of the flats & flat-darks should be the same
4) Flats should be made with the same filter as the lights.
5) Flats should not be overexposed (saturated)



Han

[Larry 1969]

There must be something wrong in the processes.

1) The gain used for the lights, darks, flat and flat-darks must be same.
2) Exposure time and temperature of the lights & darks should be the same
3) Exposure time and temperature of the flats & flat-darks should be the same
4) Flats should be made with the same filter as the lights.
5) Flats should not be overexposed (saturated)



Han

Thanks but I think I'm doing it right.
1) Yes. I never adjust the gain.
2) I don't use dark frames anymore but, when I did, the exposure and temp was the same as lights.
3) I shot the flats and flat darks at the end of the imaging session and camera cooler was still on.
4) I don't use any filters.
5) My flats were set to 20,000 ADU which is about 1/3 of my 65,000.

Larry

[Larry 1969]

UPDATE... PROBLEM SOLVED!!!

It turns out I had some loose adapters and spacers allowing my camera to rotate a bit. I pulled everything apart and put a few drops of blue Loctite on the threads then tightened everything securely. My flats seemed to correct properly last night resulting in an image that required very little cropping.

Thanks for the replies and suggestions!

Larry

[JayTee]

I would not have thought of Loctite as a solution. Thanks for this post.