I did a quick experiment with an image first cropped and then I used the cropped image as the reference for StarAlignment to crop the original. I then ran Statistics on both final images. I was only using default values for StarAlignment. The only slight difference were in the Min and Max values and those changes were very slight.
Mike,
A cropped image will match the original perfectly and is a best case (the original post was about cropping Ha to match RGB). Even so, I think you'll get a surprise if you compare your original and interpolated images pixel by pixel. Here's a PixelMath expression to try:
interpolated==original
The result is an image where pixels that didn't get changed are white. When I try this on a sample image with StarAlignment defaults the result is mostly black with a few scattered white pixels. The differences may be small, but they are widespread.
Not trying to rain on your parade but unless it was absolutely necessary I wouldn't subject my data to interpolation again after the initial alignment (hopefully against a carefully chosen, excellent quality sub.)
Cheers,
Rick.
