I happened across a way of reducing the impact of symmetrical artifacts on my images and I'd not seen the approach detailed elsewhere so I thought I would share. I was imaging the Horsehead in narrowband, and I noticed a dust donut on the almost final image and a microlensing artifact on Alnitak. I used the Game script on a starless image to isolate the artifact, then used convolution to blur it down. This reduced the visual impact of the artifacts, and I was able to create an image without the jarring effect of the dust mote and microlensing. Before and after below. Obviously better to not have the problem in the first place, but this might help if you are coming across similar issues.
