Synthetic flats

[davew]

There have been a few posts recently on the use of synthetic flats. Some say use them or dynamic background extraction in PI and some say don't go anywhere near them.

I'm in the camp that says use proper flats ! The trouble is that they don't get rid of sky gradients.

I've put together three images to show the effects of using synthetic gradient flats to sort them out.

This is a framing test on SH2-235. Could it get much worse ? If this is what you get then it's very near useless. I used the Gaussian blur method to get rid of the detail and then a clone stamp tool to reduce the light bits left behind. This blurred image was then subtracted from the light using pixel math in PI. You can use the subtract method in PS. If you take more care than I've done with these the results can be even better.

This isn't a tutorial as such. There are a few tutorials about so try it out if your sky gradients are really bad.

I hope someone finds this of some use and it could at least give hope that not all is lost.

Dave.