I packed out the lens on my FLI Microline 16 camera so the stars are fairly round in all 4 corners. Not perfect but practical.
My favourite imaging target - Vela Supernova Remnant.
This is the first panel of a mosaic (I have 2 panels so far and 4 panels from the Pentax 645 lens).
https://pbase.com/image/169341211/large
The blue O111 looks like an ants head facing you.
I have reprocessed this since posting this as I usually leave an image for a day before posting to make sure I am still happy with it (often I am not).
Looking at this image again it was too saturated and not enough of the tendrils showing up despite being quite detailed in the mono Ha and O111 images.
This version is better. Same link.
Greg.