Re: ATM Ultra-Light Dobs mounts

["Chris Westland" <westland@uxmail.ust.hk>]

 Carl:

I was going to send this off to Mel, but let me throw it up to the  list.
I think that the critical factor in ultralight Dobs is getting the weight
down on the upper tube assembly.  Mel has done a beautiful job of this with
his appleply ring and rear baffle.   Several ideas to take this a step
further

(1) graphite composite ring.  Make it "L" shaped for stiffness with holes to
lighten ... messy, but doable

(2) alternatively, use a bent aluminium tube 1" to 1.5" ... tougher to do
than it looks

(3) rather than a flat circular baffle, use louvers which overlap, and which
might be painted flat black.  This would reflect light out at a harmless
angle, and would be less likely to be buffeted by the wind.

(4) I like the idea of the "L" brackets to prevent twisting of the secondary
mount ... but why not a mount that is three dowels silicone adhered to the
back of the secondary mirror.  Wind would just whip through ... or on a
Novak style holder, drill lots of holes in the holder


As Mel noted, without the tube or shroud between primary and secondary,
baffling becomes a simpler affair ... only needed right around the mirrors.
And you have much better overall control of stray light ... in an ordinary
tube, most of the stray light is reflected off of the tube ... in the open
Dobs, it just escapes out the sides.

One problem with this openness is the observer's body heat ... perhaps a wet
suit is the answer ;-0

Chris Westland
Hong Kong (now part of China, though you wouldn't know it)


-----Original Message-----
From: Carl Woebcke <carlw@telis.org>
To: atm@shore.net <atm@shore.net>
Date: Tuesday, September 09, 1997 6:56 AM
Subject: ATM Ultra-Light Dobs mounts



>Hello out there,
>
>While I'm waiting for Mel's Ultra-Light web page to come back up, and
>for Bruce Sayre to return (If you haven't seen Mel's and Bruce's
>Ultra-Lights yet, I STRONGLY recommend them.  They're beauties!), I was
>wondering if anyone else had any plans or experience for an ultra-light
>mount for an 18" mirror (f4.5)?   Thanks.
>
>
>Carl Woebcke
>carlw@telis.org
>