Got to love Monty Python! ... and so much of their stuff is applicable to all sorts of situations.
Poking around in the shed last night I found some lengths of 20x20x1 angle aluminium and some 12x3 aluminium bar. It might take me a while to fit it in around all my other projects, but I'm going to try fabricating a mask to fit the C8 based on an aluminium frame and fishing line for the "bars".
I figure since fishing line works to make diffraction spikes when applied across the objective, it should work OK for this job as well. It is after all the edges that produce the diffraction, not the width of the bars. That being the case a fishing line mask should allow maximum light into the scope which just might make it usable on fainter stars
or with less changes to camera settings.
Al.