Quote:
Originally Posted by robz
but the specs are quite impressive (if true) : surface accuracy at least 1/16 wave RMS (typically better)BK7 substrate. 
It all sounds better than your average plate glass slab of Chinese junk does it not?  |
Only if you don't understand about the tendency in the industry for `wave inflation' via terminology. '1/16 wave RMS on the surface' translates to about 0.5 P-V on the wavefront. I recently tested a couple of 16" Chinese mirrors for a well known Australian telescope builder. They came in at around 0.5 and 0.66 wavefront . The smaller mirrors may test out better than that I don't know.
Given the issues of a relatively thick non low expansion glass it is a moot point whether such a system would benefit from a higher accuracy mirror. If you are a casual observer and not out for high planetary performance they are great value there is no argument there. As always in life , you get what you pay for and usually no more.