All our AG primary mirrors are made from Schott Borosilicate Low Expansion Suprax glass (virtually identical to Pyrex), as are all our primary mirrors on all ranges of telescopes. The mirrors are all produced to exacting standards to an F4 paraboloid configuration. How exact are they? Well, we don’t release one to our coating department unless it achieves a surface accuracy of 1/16 wave or better. How do we know when we have achieved that very high degree of accuracy?
We use one of the worlds most exacting measuring devices, a Zygo Laser Interferometer. Take a few minutes and visit the Zygo page and be amazed at just how good this machine is at measuring optics, it can measure optical distances which are smaller than 2,000, yes, 2,000 times smaller than the thickness of a human hair.
Without a Zygo or similarly accurate and reliable measuring instrument, it is impossible to give accurate measurements of an optics’ or telescope’s performance. Only the best manufacturers in the business of making telescopes use them because they are not suitable for mass produced telescopes, they are slow to use and need highly skilled technicians to operate them, it just does not lend itself to anything other than the highest quality, hand figured optics, definitely not mass produced optics to a tight budget.
The elliptical secondary mirrors are also made and Zygo tested to the highest standard, again in most instances (the larger sizes) we use Suprax to give stability and accuracy. These, along with the primary mirrors are Hilux coated for the highest possible aluminium protected reflective surfaces available.
Our 3” (76.2mm) Wynne corrector is made from very special glass types and produces the best performance you can achieve from a corrector of this size.
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