Hi Ginger,

Another quick and dirty way to remove vignetting, if you don't have a pre-made flat, is using photoshop as follows:

1. Open your original:

1. Remove the comet brightness from the image by copying small sections of the background sky nearby ( I used the lasso tool) and pasting them over the comet until you get a result similar to this:

2. Do a gaussian blur to remove the stars and create an image with a uniform transition from light to dark. I used a PS gaussian blur setting of 4.5 pixels and ran it four times followed by a gaussian blur of 50 pixels to get this result and save as the flat:

3. Do "select all" in PS of the flat image and an edit/copy and paste it into the original comet image. Do windows/show layers in PS and select "difference" in the layers tab and adjust "opacity" to your liking to remove the vignetting. I used 80% and got this result:

You could also use the flat created in step three as the calibration flat in Images Plus. Using Images Plus I got this result:

Gary

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