RE: ATM Spider Design

[epabcc@epa.ericsson.se (Bratislav Curcic)]

>> Circular vanes eliminate or reduce
>> spikes because the diffracted light is not preferentially
>> aligned as with straigt edges.
>
> If you decide to go this way, there is a good article on curved spiders on
> The ATM Page, under "Mechanical Miscellany".

If you DO decide to go that way, think again and have look into the
scopes (Newtonians or Cassegrains) of leading planetary observers.
They ALL, without the exception use four vanes.
Why ? Because you can never reach quite the same stiffness and rigidity
of spider (for given area, or cross section) with ANY other design as you 
can with four vane design. 

Thinner spiders = less diffraction.

With curved spiders you may not see the spikes, but your OTF has
invariably suffered far more compared to straight vanes that are
(several times) thinner.

Bratislav