Quattro Coma Corrector (20204)

The four-element design really cleaned up the stars across my entire full-frame sensor, and the ED glass gives noticeably sharper detail than my old corrector. Focus was dead simple once I dialed in that 55mm backfocus distance.

I shoot with a full-frame camera and was worried about vignetting, but this thing holds up surprisingly well across the whole field. Stars stay tight and round right into the corners now. The 55mm backfocus requirement meant I had to redo my spacing, but it was worth the hassle.

The stars at the corners of my full-frame shots were egg-shaped until I added this corrector, and now they're round all the way out to the edge. It needs exactly 55mm of backfocus, so budget for the right spacer, but once dialed in the FPL51 glass really cleans things up.