Re: [ATM] All Spherical Telescopes

[Delyan Toshev <delyan@trirand.com>]

> Little is known about ATMers successfully implemented any of these. One 
> commercial telescope is manufactured, based on same or similar scheme - 
> the Clavius 166 - made in France by renowned optics company.
> 

I have found that this implementation of relay telescope - Clavius - is 
design called "Paramythioti-Clave". It was even appeared on the list 
before several years. Most information about it and its implementation 
is in French, however.
I find it difficult to compare all relay variants, however. To me the 
difference is mainly in the relay-corrector system, which authors put 
under obscure patents and publications. I can sense a problem with these 
relay designs, despite their "magical" properties (fast F/ratios, small 
central obstruction, compactness) - it is the number of elements of 
relay-corrector ( 6 for Clavius ), each with two air-to-glass surfaces. 
This brings total optical surfaces, before even reaching the eyepiece or 
camera to 9, including one glass-to-mirror. It is hard to see, than 
despite the excellent field correction, how many advantages relay optics 
have, especially bellow some aperture size. May be the advantages will 
become more pronounced if such system can be made even faster (say F4), 
but is this possible?
I can suppose that the number of elements and tight requirements for 
many of the optical surfaces, despite being spherics, as well as 
mechanical properties of the OTA, pretty much limit the implementation 
of these designs for most ATMers.

-- 
Best regards,
Delyan Toshev
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