Matching star sizes in each colour channel?

[RikM]

I am working on an image of the Pacman and after a month of cloudy rubbish, I got a clear spell last night to try and get some star colour.

I used a Bahtinov mask and Bahtinov Grabber software, refocussing for each colour but checking the FWHM, there are differences between the colours. I am going to have to re-shoot it, but is there anything I can do to match up the star sizes in the colour panes? I tried deconvolving the red but I can't seem to get the right values.

Any idea what I might have done wrong in the first place? I guess I could have just botched the focus but I don't think so. It did cool during the night so I guess it could have drifted and I didn't catch it. I shot the red first so the scope would have been warmest then and cooled during that set, then been okay for green and by the blue set it was starting to mist over. ???

What a frustrating but fun hobby this is

[Shibby]

This is probably a dumb suggestion, but (not knowing what optics or filters you are using) have you filtered out IR properly if there is any glass in your train?

[rfdesigner]

Personally I would smear your sharpest RGB images down to the worst one.

Then I would combine them using LRGB combination to get it all sharp again... if you don't have an L layer then you could make one by combining your RGBs but aiming for sharpness and of course making it mono.

Derek

[RikM]

This is probably a dumb suggestion, but (not knowing what optics or filters you are using) have you filtered out IR properly if there is any glass in your train?

I use Newtonian with a coma corrector, so there is a bit of glass in the train but I also use the Baader CCD version filters, which include an IR-block coating. But thanks, I hadn't considered that.

[RikM]

Personally I would smear your sharpest RGB images down to the worst one.

Then I would combine them using LRGB combination to get it all sharp again... if you don't have an L layer then you could make one by combining your RGBs but aiming for sharpness and of course making it mono.

Derek

Thanks, I will give this a try. I don't have a proper L, but I can use the Ha stars for L and just make a low-res star colour from the RGB using bluring and a few passes of less crunch more fuzzy from Noel's action.