[joecool (Mark)]

hmmm, maybe no flat frame? Shocking vignetting... And a weird inner ring (from the lens?)

I have a CLS. Here is how I go about editing the weird white balance out in photoshop. (Oh, also, during capturing I set the 450D to ISO400 (best noise to bit depth) and force the white balance to Daylight).

Before you edit anything in photoshop drag the layer to a new layer and use Image->Adjustments->Curves and drag the line over to the left until you can see the black on the top and the left of your image from the stacking amd a thin green bar on the right. Now use the rectangular marquee tool to mark a selection which only has the clean part of the image. Now un-tick the layer visibility eye button next to this new layer and select the old original layer. Choose Edit->Copy.
Choose File->New. Create with defaults. Then Edit->Paste.

To fix the seeming lack of flat frames I saved this cropped image out to a tif file and used MaximDL to Auto flatten background...

Then opening it back in photoshop-
Now you can do Auto Tone, Auto Contrast, Auto colour.
Now Image->Adjustments->Colour Balance. You need the histogram open and showing All Channels View. Now (usually) leaving the setting on Midtones drag the sliders until the 3 colour bumps overlap.

I find this gives pleasing colours when using the CLS filter. I don't think I will use mine again though. It requires twice the expose time with my 450D which is a big negative, and the skyglow can be removed with Noel Carboni's Astronomy Tools Light Pollution Removal action.

Edit - I just tried Light Pollution Removal with Enhanced Flatten and got almost the exact same image as with MaximDL for removing the vignetting and skyglow. Hey look - more stars, less vignetting!

There is star colour in here. But no nebulosity?

Mark.