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Equipment Discussions >> Reflectors

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mark cowan
Vendor (Veritas Optics)
*****

Reged: 06/03/05

Loc: salem, OR
Re: 1/10 wave? new [Re: ausastronomer]
      #5559534 - 12/07/12 04:07 PM

Quote:

ie was it a genuine 1/4 wave mirror that was smooth, free of astigmatsm, with a good edge correction and it's only aberation was 1/4 wave of correction error?




Well, it could have astigmatism, a poor edge and not be smooth and still show "genuine" 1/4 wave performance. Errors accumulate.

But in the presence of those sort of errors, low resolution testing might easily rate it as better than it actually was (Foucault being blind to all three for the most part) and so be labeled better; in which case improving it by fixing those errors could produce dramatic results.

Best,
Mark


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nicknacknock
professor emeritus
*****

Reged: 02/20/12

Loc: In a galaxy far far away...
Re: 1/10 wave? new [Re: mark cowan]
      #5578478 - 12/19/12 07:10 AM

Well, I posted my soon-to-be-here-if-the-end-of-the-world-doesn't-come-first 12" Orion Optics 1/10 primary mirror Zygo report and reading this thread I have come to the following conclusions:

1. Mirror quality is a subject that causes friction.
2. People can have diametrically opposite views and everything in between on the subject matter.
3. Zygo reports are to be taken with a pinch of salt.
4. Nothing beats testing the mirror in the field and then experience plays a huge role in understanding if you got a good mirror or a lemon.

I will spy with my little eye and see how my dob performs, paying no heed to the Zygo report even though the test indicates a decent mirror

Nicos


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