LRGB Help.

[Tandum]

I'm still having trouble with LRGB imaging but I think I'm closing in on the problem.

I shot these last night and there are bloated stars in all the images except red. All images are only 120second exposures. I notice that the stars aren't as big in the LUM as they are in the GREEN and colour was shot at 2x2 so it may be that the gain of the camera is too high, so something like that. There is no gain setting in maxim, I believe it's set on the camera.

The result of all this is that the green and blue stars are way bigger than the red ones and you get the halo effect seen in RGB.

I was going to try again without binning but does anyone have a clue what I can try after that?

[Tandum]

I thought this might be the Anti Blooming Gates on the camera being set too low. I found an article online outlining how to adjust them but that didn't help.

What did help was adding a light pollution filter to the IR Blocker.

Does anyone know why :shrug:

Here's last nights image and tonights with the idas filter.

[Geoff45]

Is it possible that your filter set is not parfocal, in which case you would need to refocus for each filter.

[Tandum]

No, I checked each filter with the mask and they are parfocal.

Eric has kindly lent me a set of Astronomik filters so I can remove filters from the problem list. But not tonight, a storm is brewing out there :(

The huge improvement with a pollution filter in the chain has me baffled.

[edit]
It looks like it's a combination of light pollution and optics. Got the first image from the WO70 with the astronomik filters and the second from the tak, both with the idas filter.

[AlexN]

strange.. I would have though colour correction could be compensated for by re-focusing between filters.. seems not.. most of the time, from what I've seen, you can stop chromatic aberration by re-focusing, as the lack of colour correction in the optics simply makes R G and B come to focus at slightly different points... I would have thought re-focusing throug the filters would negate that issue.. Clearly the Tak image is not showing these halos, where the WO image is, meaning you've narrowed it down as far as to say the WO70ED is the cause, just finding out where the problem is, and how to fix it... You mentioned to me that CCDinspector says its slightly out of collimation.. Maybe try to do something about that? I don't know what you could do, considering the lens cell is not adjustable. Maybe shim the focuser to square it up but even that won't help if the lens spacings and matings are sub-par..

Quite the conundrum...

[Tandum]

Jeez, your way ahead of me .. I'm just happy I got decent images from any scope at the moment :) I got a lot of other stuff to check out before I start playing around with the newest scope in the stable :D