Re: ATM 10" Flex Mirror

["William Kelley" <wekelleylwk@sedona.net>]

Congratulations Dennis,,

You have joined the growing ranks of ATMers reporting excellent results with
flex mirror scopes.
BTW, the 6" F8 spheres being sold by Bill Vorce all seem to have very good
spherical mirrors.
I've tested 9 of them and think they are very good value. IMHO they should
be flexed with just
a bolt bolt epoxied to the center. This approach will convert the 1/4 wave
correction of the
unflexed sphere to about a 1/12th wave when tensioned. More than good
enough, and a very
simple way of making up a flex cell.

If you are filtering the air on the 6," a similar set up on a truss tube
should work equally well.

I'm looking forward to your adventures with the 10" F6.

Regards,

Bill Kelley

----- Original Message -----
From: Dennis Woos <wooscons@sover.net>
To: ATM List <atm@shore.net>
Sent: Thursday, October 18, 2001 1:35 PM
Subject: ATM 10" Flex Mirror


>
> 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
>
>
>
>
>