UV/IR Block at F2

Any old UV/IR cut filter should work.  What matters more is the size of the filter because the RASA has such a big light cone, and you will want to avoid reflections.  I would think a 36mm filter would work but you may want to try a 2".  Either is very affordable.

Steve:
Thanks for answering. I was thinking about the incident angle and bandshift and did think I was probably worrying too much when I couldn't find any info out there.

Hi,
Angle of incidence is only a consideration for narrowband filters (Ha, Oiii, Sii, etc) where if the angle is too far off from what the filter is designed to pass, some of your light will cut off, with more an more being lost the farther off the angle is. Not a concern with broadband filters (R, G, B) or rejection filters (IR/UV block).
CS,
Arnie