Is the green channel automatically selected from FITS files when doing photometry?

[padraig houlahan]

I'm a little confused by the green channel extraction references. They seem to be focused on DSLR and OSC images, and the implication seems to be that the green channel extraction is mainly for those images. Hence my question: when using FITS images, is the green channel automatically extracted or do I have to do something explicitly?

Thanks in advance for responses.

[han.k]

It is an manual action. See popup menu of the photometry tab. See attached screenshot

Cheers, Han

[han.k]

Select first the files (ctrl+A) before using the menu

[padraig houlahan]

The pop up result says extracting is only allowed for OSC images

"Skipped COLOUR image C:\Users\pjhmx\Downloads\aeumafits\Stacked_6_Unknown_20.0s_IRCUT_20250526-210312.fit, Raw red, green or blue pixel extraction is only possible for raw images."

[My images are from a Seestar50.]

[han.k]

The images should be raw, so still without colour. Can you attach one image so I can have a look?

Han

[padraig houlahan]

Here's one.

P.

[han.k]

That image is no longer raw but already transferred in colour. Photometry is only accurate if you use the original raw images. They will look like gray images with a kind of checker pattern.

Only after splitting the raw images you can safely (for photometry) stack them. So green sensitive pixels stays with green sensitive pixels. All are grey images.

ASTAP will split your raw image in a TG, TR, TB image. Use as a start only the TG images since that is 50% of the original images. The blue (TB ) and TR (red is only 25 % of the original pixels. Image will also reduce to 50% size after splitting.

Han

[padraig houlahan]

Thanks, Han.

I'll dig around some more then.