|
AFAIK it is much harder to make a ~99% reflectivity mirror than prism. A high quality prism diag is probably your best bet. Chromatic aberration is the only downside of prisms vs mirror. I believe that in high quality diags, crystalline materials like quartz are used instead of glass to minimise CA. (But for a Ha solar scope CA is a non-issue, as the image essentially contains just one colour.)
Another plus for the prism diag is that it does not degrade with time as mirror coatings eventually do.
|