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quartz or pyrex secondary

Started by Dasuhu, 04/27/2002 09:00AM
Posted 04/27/2002 09:00AM Opening Post
I was looking at secondaries from protostar and noticed that the quartz mirrors were twice as much. What exactly is the difference? Is it worth the money, or is there almost no difference from quick glances?
Posted 04/27/2002 09:59AM #1
The price difference varies, but it is pretty painful, particularly in the 1.3" size.

Supposedly quartz takes a smoother polish, and each of the quartz secondaries is individually tested and comes with an interferogram. The regular Protostar secondaries are random-sampled for intereferometric testing and 100% tested on a reference flat. So, some of the price difference is the cost of individual interferometric testing.

I see the ULS Quartz option for planetary observers who will do just about anything within reason to improve contrast and are willing to pay extra in the attempt.
--
Mike