The (continuing) FLAT Challenge. :D

[Macavity]

OK, this might be a bit boring (impossible)! But I am still working
on possibility for *general* method for H-Alpha Flat production!
(Notably when the Solar Disk is surrounded by random dark sky)

For my un-Barlowed Lunt 50 / DMK41 images, I can "get away"
without FLATs (Dodgy pixels avoided by image placement too!).

BUT, for 2x Barlowed images, I do get the dreaded DUST motes!

QUICK CONCLUSION: Over a limited area both Dust Motes and
"Chip anomalies" are *well* corrected by the "Cling Film Flat"!
Where there is a dark area around the sun, it works less well...

Aside: I now note that *centering* the solar disk before taking
the flat improves thingsl It almost works for *general* images.
Unfortunately my Sun doesn't QUITE cover the full frame tho!

<thinks> Maybe I can "drift" the flat to get uniform coverage?
Or (sufficient light allowing) apply a SECOND layer of cling film!
Might reduce some "material directionality" in the light scatter.

***********************************************

Firstly, an initial Barlowed Images (no Flat) showing ALL crud:
(Note BLOBS and the dodgy region of "rasterisation" at top!)



Applying a single layer of CLING FILM show this stuff on the FLAT!

The following shows the OFFLINE (AutoStakkert) Flat Processing:

The following shows the ONLINE  (FireCapture) Flat Processing:

BOTH images show good removal of sundry gremlins via application of a FLAT!
The bright edges on the solar limb are somewhat less using real-time removal.

....

THEN I thought I might try to produce a General FLAT by centering the Sun:

Unfortunately my scattered sun *almost* but not quite covers the total area!
This is evidenced when I apply this *general* flat to the first (specific) image:

 

No "Free Lunch" yet! But I think But I now better understand what is going on.
One senses the density / scatter of the material is both critical and fortuitous!