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What is “certified”? It seems as if a lot of so-called manufacturers are selling optics that they claim are “certified”. I also see this term being used on the “re-sale” sites on the web, but exactly what is certified?.An optic can only be certified if it is tested against a known reference element that is traceable to a bureau of standards that is recognized by the optical industry. These reference elements are used in interferometry. Yes, it is very expensive and time consuming. Yes, it is the only way to know for sure just how accurate an optic or optical system is. Don’t be fooled as there is no substitute!.Data reduction done with the Foucault tester at Radius does not, and never has, “certified” any optic. The P-V numbers attached to these so called “certified” optics done by others will seldom if ever come close to the data results done with interferometry. These exaggerated claims are more of an indication of a complete lack of optical testing knowledge on behalf of the manufacturer and down-right dishonest if you ask me.Our experience has shown that large (more than 12.5") and fast (f/5 or less) mirrors tested at Radius (with a Foucault tester) will suffer from under correction on the edge up to and sometimes exceeding one full wave!. Don’t believe it?, just ask any qualified professional or better yet, have that mirror you paid top dollar for tested by interferometry. You will always receive honest, reliable and accurate data with my optics!.
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