H Alpha filter query

Kieran is that the 6nm version? If so it may be that there isn't enough light hitting the CCD to lift the background and the banding is the cameras response to this. I read this somewhere before maybe ukastroimaging. Sounds plausavble to me. Try rotating the camera the other way and see does the gradient reverse. If so then I'd say that's your problem Solution: expose for a LOT longer. Till you get the background levels up a tad if possible.

Think I found the prob. Just checked some old dark frames:



Looks like H Alpha for the ccd is just too low to get away from the build in noise. Damn, I will now have to waste time on dark frames, as if H Alpha wasn't hard enough.

Kieran,

I have to say thats a very strange looking dark frame. If never seen one quite like that before.

Here's what a stretched stack of darks look like on my ATIK16HR.

Of course you should be able to get away with taking one set of darks and use these for the H-Alpha images. I wouldn't imaging it would change too drastically given the range of temperatures we get.

May have a light bleed. But I also had to get the capacitor in the ccd upgraded due to saturation bleeding. Hmmm. Time to experiment I think.

May have a light bleed. But I also had to get the capacitor in the ccd upgraded due to saturation bleeding. Hmmm. Time to experiment I think.

You read my mind, it does look like a light bleed from somewhere, like Dave said thats one very unusal dark frame, it doesnt look like thermal noise, could it be some sort of noise thats generated when the CCD is read.??