Quote:
Originally Posted by Gama
All you require is PV 1/4 wavefront error, as was said, so less time is spent getting the surface to a higher degree, which you will not see in real life anyway due to atmosheperic seeing.
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Its not so much a matter of atmospheric seeing. Even in poor seeing a better mirror will have more moments of sharp detail for planetary viewing. The point is that at prime focus deep sky imaging you don't have enough image scale to differentiate between a 1/4 wave wavefront and 1/10 wavefront optics. Planetary imagers typically use effective focal lengths of 10 meters or more to exploit the quality of their mirrors.
The other issue is central obstruction. A high quality 0.95 Strehl optic set and a mediochre one ( say 0.8 Strehl ) are both degraded to the low 70's and mid 60's Strehl ratio by a 45% obstruction...
That is not to diminish the task of making a truly 1/4 wave wavefront RC optical system. These mirrors would be much more strongly aspheric than your standard Dob mirrors. If they can actually pull this off at that price it will be a modern marvel of the marriage between technology and cheap labour.
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