Re: ATM 10" Flex Mirror

[Dennis Woos <wooscons@sover.net>]

A note about the filtering.  We got a filter for our surplus computer fan
from www.cyberguys.com, search on FILTER.  This is a nifty little filter
attachment, and you can use other filter material than what is included.
Also, we bought a bunch of AA NiMH batteries from
www.thomas-distributing.com, and these are great.  Eight of them seem to run
the fan forever.

Dennis

Dennis Woos wrote:

> 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