Misalignment of colour planes with webcam imaging

I have noticed with a number of my webcam images (Venus and Jupiter) that when I capture an image there is a reddish hue on one edge of the planetary disc and a blue hue on the opposing edge of the disc. I wrote this off as chromatic abberation of my cheap barlow. But I observed a similar phenomenon when I recently upgraded to a Televue 5X Powermate.

After a little investigation I have come to the conclusion that the colour planes from my Meade LPI are not pefectly aligned until I perform some correction. This may be the case with other (or even all) webcams.

Has anyone else experienced this?

I now, for example, take the three colour planes from the output of Registax and reallign them (can be done in registax or I sometimes use the Meade image processing software) then produce my final image which is without the colour fringing.

Also, I'm wondering whether I should realign before I do *any* wavelet or other enhancement processing - is there any difference in effect? (okay, with experimentation I can ascertain this myself - but someone might know of the top of their head).

I'm also wondering (secondary topic) in whether post-capture enhancements should be done independently per colour channel. I had one image of Jupiter (prior to learning how to collimate and prior to acquisiton of my powermate) which appeared to benefit from more aggressive wavelet processing of the blue channel.

Any coments would be welcome on the fringing or whether there is value in processing the colour channels seperately.


Mark

Do you get the same effect when looking at objects higher than 60 degrees from the horizon?
It would be worth testing on a bright star at 15-20 degrees up and comparing that to a star 60 degrees up.
I'd bet that the low

You may be falling victim to the effects of dispersion, looking through the lower layers of atmosphere.

I've seen this effect as well with webcams.

Another testing method would be to rotate the imager and take another series of images. If the imager is at fault, the colour problem will not change orientation with the camera.
If it's atmospheric, the same limb of the planet will have the colour cast.

Cathal - excellent comment and suggestion!
Yes I'll try rotating the webcam and see if fringe follows.
Your explanation may well prove to be the cause of the phenomenon.
Look forward to some experimentation...

Mark

I saw the same effect with my LPI which I put down to the Bayer filter on the CMOS chip. If you have to make the same colour plane alignment all the time then its probably this. You could check some old raw images and manually adjust one, remember the adjustments and then check others to see if they get aligned. Saves having to wait for clear sky.
The R,G & B wavelengths will also travel through the optics on ever so slightly different paths which may also add to the offset.