Quote:
Originally Posted by AG Hybrid
Hubble Optics mirrors have been tested and had their results posted on Cloudy Nights. The few that have been done are test around the 0.90-0.92 Strehl mark.
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You would need to qualify that: were they mirrors in the larger ultra fast sizes like F3.7 ? And who did the tests - was it with a foucault test ? Or Null interferometer . I would go further and say that an true 0.8 Strehl mirror free of significant figure distortion problems in a large fast size would be a great performer . Unfortunately I've found a number of epic fails in 20" + sub F4 size amongst a number of USA makers - I would be very surprised if a Chinese company were doing a lot better for half the price !
The fact is that large sub F4 mirrors are much harder to make well - polishing and testing techniques that work easily for smaller slower mirrors can start to fail when applied to larger mirrors - no matter how great your enthusiasm might be .