ATM 10" Flex Mirror

[Dennis Woos <wooscons@sover.net>]

As our 6" f/8 flex mirror dob performs well, my son Doug and I are going
to try our hand at flexing a 10" f/6 plate glass mirror, 7/8" thick.
While we are grinding the mirror, we have started to think about a
couple of issues.  1)  Should we build with sonotube, or move to a new
(for us) truss-tube design?  How well would a truss scope work with a
relatively light mirror?  Is it worth the extra work?  2)  If we build a
truss-tube scope, then how does the problem of bringing/keeping the
mirror at ambient change?  For our 6", we followed Adler's example and
have mounted a fan blowing across the mirror.  This works well.  If we
go with a truss design, then do we still need a fan blowing across the
mirror?  If we do, then it does not seem possible to filter the air, and
this doesn't sound good.

Any and all advice will be appreciated!  BTW, here is the low-down on
the 6" f/8.  We bought the spherical mirror, mirror cell, spider, and
1.5" secondary from Telescope Warehouse for $100.  Of course, we didn't
use the mirror cell, and the secondary is a bit too large but we used it
anyway.  The diffraction rings look to us to be identical both sides of
focus. We can see Trapezium E pretty easily, and we have seen F.  Four
moons of Saturn are pretty easy, and it seems that with averted vision
other moons are just visible, but this may be our imagination.  The
Cassini division is very black and clearly seen all the way around, and
there is other stuff going on in the A ring.  There is a lot of detail
visible on Saturn itself.  We need to observe/learn more of Saturn to
say more.  Shadow transits on Jupiter are easy, and the GRS is visible
but washed out.  In fact, all color on Jupiter is kind of washed out. at
least compared to what we expected.  However, we recently looked at a
CCD image taken through a Zeiss 6" f/15, and it was very similar to what
we see.  Anyway, we are happy with the scope, and are looking forward to
pulling the 10"!

Dennis and Doug