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Bill,
I've made a series of wire spiders over the years
using 4 vanes/8 wires and they have all been very strong and stable. No
breakages either. I plan to put a series of pix and plans up on my web
site soon. In the meantime the basics are:
The scope is a 10" f/5 newtonian flying scope - I
took it to table mountain this past summer for those who were
there.
I use a central hub to which the wires are
attached. This hub is basically a rectangle of Delrin black plastic which
allows me to isolate one side electrically from the other. The wires are
attached to the edges by wrapping around small bolts. It is important to
attach the wires off axis as this creates a very strong stable
arrangement. See Mel's modified spider on his 20" for an idea of what I'm
talking about. I start the .014" music wire by wrapping around the bolt,
out to the threaded fork (a clevis from a model airplane) back to the bottom of
the hub, back out to another clevis and back to the bolt which is then tightened
around the wire ends. Repeat this on the other side of the hub and you
have 4 vanes on the hub. The diagonal holder is attached to this with a
standard 4 point collimation system. I'll try an ASCII picture
below. Hope this helps. I hihly recommend this design. It's
very stable and low profile. The spikes are very thin and long.
Collimation of the hub is deceptively simple. I'll let you know when
I get the page up on my site.
The hub as seen looking down the optical
axis.
/ To clevis
bolt /
_______________[_]_\ /
__1/4" Delrin sheet__ ]
X The wires cross optically here and must line up with
[
] / \ the other returning wires below
the top wires (see below)
\
\ To clevis
___________________
0 |-------- ASCII wire (not a great
way to draw them!)
bolt
| --------------
|
O--------- clevis and tensioning bolt
| --------------
__________________|--------
Hope this makes sense.
Ed Stevens
http://www.flyingscopes.com
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