Re: ATM Spider Design

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

Ken Florentino wrote :

> If thermal effects were there you could see them. Take a bright star out
> of focus and blow across you tube. Now that's thermal effects!

So that's what it was ? Thanks for the enlightment ! Danjon and Couder
have been writing about spider thermal effects many decades ago, but then,
who has heard of them ??? And, yes, I guess that if YOU don't see 
something that must be a definite proof that it doesn't exist. 
May I suggest that you get a digital thermometer next time and measure
air temperature inside well cooled (equilibrated) telescope tube. Then 
measure the temperature of one of the vanes.
Oh my, they are COLDER that the air !!! How come ?

> By the way, I made a 3 vane support about a year ago and like it just
> fine. It takes a bit of getting used to 6 spikes, but I've come to like
> it. Also, each spike has half the energy of the spikes in a 4 vane so they
> are dimmer.

By the way, you have also lost more than 10 times in torsional
stiffness compared to properly offset four vane. As you are "empirical"
man, I won't talk about any of the theory behind it. Just make two
spiders, one with your recipe, and another a'la Texerau (offest four vanes)
using vanes that are several times thinner; adjust them roughly to the same 
tension force. Then grab the secondary holder and twist and pull. 
Surprised ?

Bratislav