Re: (ATM) Spiders

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

I think we're getting little bit carried away too far.

Yes, difraction effects are deterring. Yes, wire spiders have less
difraction (and refraction induced effects from a surrounding cold
air). But these effects are EXCEPTIONALLY subtle ! Parker uses 
quite ordinary metal blade spiders. Miyazaki (I got it right this 
time, didn't I !) does the same I think (but maybe 3 blades instead 
of 4?). Same with professional scopes. There is a LONG way to go before
you get any benefits from improved spider design. Roll up your sleeves
and make those primaries real GOOD. Be patient and wait for that scope
to cool down. Be EXTREMELY patient and wait for that 1/2 hour in a
year when seeing is 10 out of 10, and then MAYBE start worrying about
that 0.1% improvement in contrast that you _might_ get.

Bratislav

PS of course, MECHANICAL benefits from better spider design are of
primary concern! If your secondary wobbles and oscilates, change
the spider design by all means. But do not expect that your scope 
starts showing Hubble like images just because you put in some 
wires instead of boring old blades