Affinity Photo 2 stacking Mac - Flat file oddness

[engstrom]

Still a novice so this could be a stupid question.

I captured some flats after an imaging session the other night. The original lights were captured in Ekos but the flats I captured didn't actually seem to capture anything. I then captured more flats in ASI Studio and they seemed ok.

When I stack these in Affinity photo the red and green channels seem ok but all the blue data is stacked to the extreme left i.e. level 0 of the histogram is reporting 518000+ pixels in the blue channel (I'm assuming this is reporting clipped data).

Presumably some mismatch between ASI Studio and affinity might be the cause of this but has anyone else had this issue or similar? Anyway to recover?

The resulting flat is yellow. I'm assuming this will adversely affect the eventual stacking?

[Elp]

Not sure how affinity stacks the data but from my experience using DSS and Siril your calibration files can remain mono/non debayered and you can calibrate fine as long as you tell the calibration process to debayer the data into RGB colour as the output with the debayer pixel layout which matches your camera (most common RGGB).

If you've taken the flats correctly each RGB peak should be closely aligned near or below the halfway point on the histogram.

[engstrom]

1 hour ago, Elp said:

 

If you've taken the flats correctly each RGB peak should be closely aligned near or below the halfway point on the histogram.

When I was taking the flats the histogram looked ok on ASIImage. When stacking in affinity (and viewing them in several fits viewers)when the flat frames are loaded prior to stacking they have just the green and red in the right place.  If I use the ASI fits viewer the flats also show up as yellow and looking at the histogram the blue is there but seems to have been clipped from the final image. If I then press the auto wb button in that app all three channels line up and show a mid-grey(ish) image. It seems like the image is capture and balanced but when saved something goes wrong and the WB is off although the image thinks it’s ok (maybe).

Changing the WB options in Affinity don’t seem to have any effect. 

Edited March 28 by engstrom

[Elp]

7 minutes ago, engstrom said:

Changing the WB options in Affinity don’t seem to have any effect. 

Not even if you save the corrected WB flat as a new file?

[engstrom]

44 minutes ago, Elp said:

Not even if you save the corrected WB flat as a new file?

Handily the app doesn't let you save a corrected file as a fit.

I'm just about to try as an unstretched, auto WBed tiff. 
 

loading an un-autostretched but auto WBed tif into affinity now shows all three channels but they’re too far from the left (which makes sense…I guess…if they’re not stretched).

The pain in the bum thing is you can only load the fits in singly to the asi viewer before saving them out…

And there doesn't seem to be a way in the capture app to specify what WB to use.

Edited March 28 by engstrom

[Elp]

I haven't used it but if it's anything like Firecapture there should be either an auto WB setting or you can set it. Think I saw it in a thread recently where someone was having an issue with unexpected colours.