You can tens all you want, or even twenties. ;?} But take a look at John
Brooks' article "Structural Considerations for Telescope Makers," _Sky
and Telescope_, June 1976, pp. 423-8. As for the vibration
characteristics of metal, there's a reason why they don't make bells out
of wood. Wood tripods are expensive, but there are advantages to them.

Cheers - Chris


How many do you see supporting really large telescopes?

Depends, I suppose, on your definition of "really large." At a certain
point wood for the same stiffness coefficient becomes too massive to
move around, and the beauty of a wooden tripod lies in its portability.
If you don't have to move a telescope then you can beef up the mount
with metal beyond the point that wood might be conveniently used. I
remember back in the 90s seeing a guy advertising his portable
astrophotography setup - it was a newtonian in the 12" range set on a
beautiful german EQ mount, a questar maybe, on a portable short tripod
made out of hardwood. The pictures he took with it were fantastic.
There's more to astronomy than imaging, too. Some people simply like to
look through their telescopes, and pound for pound wood is a better
material for building a tripod than metal. It weighs less and dampens
vibration more. It's not as durable, but it works well.