Flat overcorrection - optical flaw - can PxI rescue me?

[rbotero]

Hello PixInsight Gurus

Some of you may have seen my post here:  https://www.cloudynights.com/topic/579268-field-flattener-help-me-save-1k/ so bear with me...

I think I have identified that my early 90s 4" field flattener causes reflections in my imaging setup:  Moravian 16000 CCD + Astrodon filters.  The reflections, if that's what they are, manifest in my images as a bright (large >1000px in diameter) centre spot that is not fully corrected by applying flats.

I cannot get rid of the reflections mechanically - i.e. I have flocked the interior of all couplers, removed any sag, taken flats using different panels, sky, etc - but am reduced to rely on software to flatten my images and this is very object dependent (on top of being extremely frustrating!  ).

For example the hot centre spot is very apparent here:



But less so here:



The best solution I have found is to use Geert Vanhauwaert procedure whilst calibrating in PixInsight as described here:https://pixinsight.com/forum/index.php?topic=9312.msg59752#msg59752.   
I have tried not to clip my backgrounds but I'm afraid I have ended doing so to hide my problem. 

Can any of the experts suggest other methods to try to remove my calibration issues?  I am posting 10 (each) raw light, flat, dark and bias frames in Google Drive folder if anyone wants to play with them.

Files here:  https://drive.google.com/drive/folders/0Byu0GAFkH71VUk02dzFOOUlxX3M?usp=sharing

Thank you

Roberto

[Niall Saunders]

Hi Roberto,

You might want to add to that folder the xpsm files associated with your calibration processes, along with a brief document (or associated notes within the XPSM file(s)) describing the method and sequence that you implemented.

You might also be interested to see the dramtic improvements made to some of the calibration processes that will be available with the imminent release of the latest major version of PixInsight. Perhaps these new tools will eliminate your problems once and for all 

[rbotero]

Hi Niall

Thanks. I've attached the xspm file with my calibration modules.

Roberto

[rbotero]

And for completeness here are the modules I use to create the master calibration files.

[rbotero]

Now attached, sorry.