debayered images have pink stars?

[troypiggo]

Doing some testing with my 5DII at home (light pollution and near full moon) before I get to a dark site next weekend.  Using Sequence Generator Pro for image capture, and have set it to capture single image (CFA fits).  I used ISO 1600 and 5min subs.  The raw subs are pretty overexposed backgrounds as per the attached image with no STF applied, and before debayering.

Using BPP and ticking the CFA option, the output debayered images have a blue background and the stars are pink.  See attached image.  I am pretty sure I've used all the correct bayer pattern settings (RGGB, VNG etc).  Tried all other combinations and all wrong.

Any ideas on the cause and cure?

[TobiasLindemann]

Maybe a stupid question, but do you have color calibrated your image. Even if so, IMHO it looks like the pink stars are saturated in the raw image, so it is hard to color-calibrate.
More questions: Is this a modded DSLR with absolutely no low-pass-filter? If so, maybe a IR-UV-cutfilter (e.g. Baader L) will help.
Can you upload a raw, or fits image somewhere?

[troypiggo]

As you say, the stars being pink made it hard (for me) to calibrate.  It's not a modded camera.

Here is a calibrated and cosmetic corrected single sub, and also a debayered sub.

https://www.dropbox.com/s/jq69ayzvobiatmd/Antares_300sec_1x1__frame1_c_cc.fit
https://www.dropbox.com/s/4whpafoqr4jiulm/Antares_300sec_1x1__frame1_c_cc_d.fit

I couldn't register them due to PI only being able to find 2 or 3 stars, so can't get it to stack.  That's another problem.

[troypiggo]

Been doing some more testing tonight.   Seems there's a definite issue of overexposure.  I'm used to using my QSI583ws and know how long I can expose on that.  Have no feel for the ISO and exposure lengths for the 5DII.

Have dropped the ISO and exposure lengths, and while there are still the pink stars, the background is more manageable.  I'm playing around with HDR Composition to try to tame the pink saturated stars.  What's happening in the R and B are near saturation, but because the bayer matrix has 2 G's, it's not quite so bad.  I'm assuming that's what's going on.  So the saturated stars are this pinkish/magenta colour.  I think.

More testing and will post results.

[Alejandro Tombolini]

Doing some testing with my 5DII at home (light pollution and near full moon).
I used ISO 1600 and 5min subs. 

Definitely the exposure time is huge. In that condition and ISO your exposure time should be between 15 and 30 seconds.

Saludos, Alejandro.

[Ignacio]

I use 5-minute iso1600 exposures all the time with no problem (even 10 minutes in some objects). Looking at your undebayered calibrated image, it is plagued with dark dots, so it seems you have a calibration problem of some sort.

I suggest you try calibrating one sub manually (using ImageCalibration), after inspecting your master calibration files. There is also evidence of an incorrect master flat division in your image.

Ignacio

[troypiggo]

Thanks mate.  Looking into it.