SharpCap+SeeStar=Wrong Colors

[Cey42]

I have a new Seestar and I managed to point SharpCap to a folder on the Seestar in order to do live stacking. The problem I am having is the colors are all wrong. I have tried the auto color buttons and manually moving the color sliders but I cannot get close to the right colors for M27. Is there an issue in fits files? You can find the files here https://1drv.ms/u/s!AmzOfpCoABCRgfs4gev ... Q?e=SkiWye

Here is the image as seen in the Seastar app with the colors as expected for M27

M27.jpg (100.95 KiB) Viewed 11150 times

Here it is in SharpCap

M27b1.jpg (57.73 KiB) Viewed 11150 times

Thanks,
Cey

[admin]

Hi Cey,

the problem is with FITS files that there is no perfect agreement on how they should be interpreted - I have to have an option in SharpCap to allow the bayer pattern headers written by SharpCap to be flipped for compatibility with different processing applications (see https://docs.sharpcap.co.uk/4.1/#Bayer% ... %20headers). I suspect that the way that the SeeStar is writing the files is the opposite of the way SharpCap is expecting. If you could send me a file I will check the headers and see if I can find a fix that doesn't break other things.

As a workaround, you should be able to set the 'Debayer Preview' control to one of the 'force XXXX' options to correct the issue. The pink you are seeing is a common consequence of the pattern being flipped in either horizontal or vertical (ie RGGB used when it should be GBRG).

cheers,

Robin

[roelb]

I have checked the FITS header and the the Bayer pattern is: GRBG.

When I change that in the SC Debayer Preview, stack & do auto color & some histogram adaptions, the following image comes up:

Capture_Folder Monitor Camera_45 x 10,0s = 450s_24_10_2023T17_23_31.jpg (172.02 KiB) Viewed 11116 times

[roelb]

And here with a slight color change: lower the Green color with 2 "micro steps":

M 27 - GRBG - Histogram + Color changes_Folder Monitor Camera_45 x 10,0s = 450s_24_10_2023T17_44_07.jpg (938.89 KiB) Viewed 11111 times

[Cey42]

Thank Robin and Roel! I am so excited to see this is just a parameter change. The ability to do Live-Stacking on the Seestar has now greatly improved the scope.

[admin]

Hi folks,

that's looking good - glad it is all working now. Do send me a FITS file if you can so I can work out if the fix can be built in (depends on what headers are written to the FITS)

cheers,

Robin

[Cey42]

My original post has a link to the files. Does it not work for you?

Thanks,
Cey

[admin]

Hi,

sorry, I missed noticing the link. Too busy looking at the pretty pictures I guess

The raw FITS files have GRBG set as the bayer pattern, now, that's correct for a file that is being interpreted as starting top left, however...

* Correct FITS behaviour is to start the image at the bottom left
* SharpCap has always started top-left for historical reasons, and it's too late to change now as it would break workflow for everyone using FITS in SharpCap
* SharpCap knows that it's doing the wrong thing and therefore that it has to deal with reading files that are written properly, so it makes adjustments to deal with the issues

In this case the adjustments are incorrect because the SeeStar FITS file is wrong according to the strict FITS spec, which means that the fix SharpCap does to the bayer pattern that would make things come out right for a correctly written fits file breaks this one. Sigh...

Unfortunately the Seestar is not adding the (relatively new) ROWORDER=TOPDOWN header that would allow SharpCap to detect this situation and fix it.

The only thing left is to look at the 'CREATOR' header and add special case code if the seestar is spotted, but I'm kind of reluctant to do that sort of thing if I can avoid it. It means things don't quite behave the way that they should according to the documentation for no immediately obvious reason.

cheers,

Robin

[Cey42]

I agree with you that you should not add code to fix this special case. It is an easy thing to fix by setting the correct Debayer pattern manually. I will send a bug report Seestar about including ROWORDER=TOPDOWN header.

Thanks,
Cey