Quote:
Originally Posted by SkyViking
Is that based on empirical testing or is it gut feel? I'm asking because I just can't get the math to stack up in favor of flat mirrors at all.
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I'm not arguing against flat mirrors. I know for a fact that the 16" Conical design that is available is pretty hefty in the central half ( I've put his up on the test stand ) and Anthony Wesley's actual cooling data show it is a poor candidate for planetary as he can't get it to equalize quickly as other 16" that he has .
My experience on the 12.5" to 14.5" re weight is just that I have made a number of them - I felt the 14.5" was not too much different in weight than a standard 14' but that was just my feel. Next time I will put one on the scales
They are definitely more fiddly to make due to their propensity to rock on the polishing turntable - very hard to hold properly without twisting and the design that has been floating around for 30 years - as sold by Royce is pretty thin on the edge and can easily become astigmatic or irregular distortion during polishing and needs close monitoring. Only careful monitoring of the star image under optical null during manufacture gives this information - not something that most manufacturers do. I found 14.5" quite susceptible to distortions even during final figuring so polishing load has to be kept to a bare minimum.
So in essence they are far from ideal to work on from an opticians point of view which is probably one reason why everyone does not offer them .