I've finished my project after lots of experiments, i tried etching cream on glass but it always ended up blotchy, any way i found a glass place that did etched glass which has hardly any grain, they cut it to circles of 90mm in diameter and drilled 4mm hole in center, i then attached it to a model aircraft propellor mount which fits snug on a cd motor, i have a crap achromat at the moment which means i need a long extension tube from my V1E.
anyhow here are some pics
anyhow here are some pics