CCD Colour Channel Issue

[deadsimple (Ash)]

I've been imaging Jupiter for a few weeks now and I seem to have a huge discrepancy between colour channels. Green is the best quality as you'd expect, Red is very saturated and Blue is an awful mess.

Now I've read previous threads (like this link) that hint at blue channels being sensitive to seeing, but I actually have increased graininess and chunkiness in the blue channel - it's not just a matter of detail (which indeed is bad anyway).

Setup: 200mm f/6 newt w/tracking, SP900NC webcam, Baader UV/IR filter.
Camera Settings: Brightness: 50%, Saturation: 88%, Gamma: 0%, Shut: 1/33, Gain: 45-65 (when using 3x Barlow), 5-10fps.

I can't work out whether it's my colour settings for the camera, the camera itself or the Baader filter causing issues. I've tried changing the framerate on the camera to rule out excessive compression.

The first image set (below) was captured at 10fps with a 3x Barlow. Second set was captured on a different night at 5fps with Barlow at 4.0x - the blue channel on this one is ugly!

If anyone can give any insights as to why the blue channel is rubbish and the red so saturated and detail-less I'd appreciate it!

[iceman (Mike)]

Hi Ash
I've been away so didn't see this thread until you pointed it out in the other thread.
The blue channel is almost always the worst - it is the most dependent on the seeing due to its shorter wavelength.

I've had many nights where the blue channel is horrible, but on the nights of good seeing it can contain quite a bit of nice detail and contrast.

You could try without the UV/IR filter to see if it makes any difference, or to see if you've got a dud filter.

But part of the problem of using a 1-shot colour camera is that you can't change the gain or any other settings for each colour channel. You have to adjust it to about right, and then each channel can get its own adjustment in post-processing.

I think it's just a matter of patience and continued practise. What you're doing now is practise. You need to wait for those nights of good seeing and that's when all this practise will bear fruit and you'll get an image you'll really be proud of.

[deadsimple (Ash)]

It almost seems as if the camera gets very little blue light and has to compensate with the white-balance settings, just boosting the graininess of the little signal it has in that channel.

Originally Posted by iceman

You could try without the UV/IR filter

Yes good idea, I might do that. I was just hesitant to do this earlier as I don't want the CCD chip exposed for too long without a filter protecting it from dust. Seeing as the problem is serious enough I think I have no choice now.

But yes, I've solved the red channel saturation at least with a lower WB-R slider value.

Thanks.