How I repaired my Ikelite 8 inch acrylic dome port with micro-mesh pads and polishing liquids.
A set of micro-mesh polishing pads, and a scratched dome. Pads from left: 1500 is the coarsest and you begin with that, on the right the finest grade 12000 which is used for finishing.Here you can see the small scratches everywhere. Well, actually they are very hard to see on a photo, you more like feel them with your fingers, and see them in your pictures taken though the dome.Start with the 1500 grade and wipe into a single direction  only. Then take the next grade and wipe at 90 degree angle across your previous direction. Continue until you reach the finest grade 12000.Use water at all times to clean off the small particles that result from sanding the dome. At first the dome becomes matte, but do not fear, it will come bright and shiny at the end. Just be patient.Now the scratches are gone after griding with grades 1500, 1800, 2400, but the dome looks like this. So you need to keep on polishing with finer grades to make that dome transparent again.After the finest grade 12000, it should be crystal clear again.After this you can use Acrylic polishing creams to make it really shiny. Here I am using the Novus acrylic polishing set, and starting with the #3 cream.Then Novus #2 cream.Finally Novus #1 cream and polisihing with a soft cloth.Now it looks like brand new again. The whole process took about an hour.You can do this probably many times over, and it isn't too hard.