Re: ATM 6" Dob: How Easy? How Cheap? How Heavy?

[Brent Hutto <BHutto@InfoAve.Net>]

What an amazing number of replies so quickly, both to the list and
directly by E-mail! I'm not going to be able to reply individually to
each person but the assistance is very much appreciated. To answer a 
couple of questions posed in several replies, I'm not going to grind 
a mirror and I do already have a couple of eyepieces that I use with
my 60mm refractor (25mm Kellner, 9mm Kellner and a brand-new 
University Optics 7mm Orthoscopic).

The prevailing opinion seems to be that 3/4" plywood as specified in 
the SF Sidewalk Astronomers plans could probably be reduced somewhat 
on a 6" f/8 scope but solidness and stability is necessary and a 
reasonable weight could be maintained with something close to those 
specifications. Also, putting screws into thinner plywood doesn't 
always work out well. I'm visualizing a slightly more elaborate 
design with thinner plywood but square pieces of wood inside the 
corners so that no screws have to go end-wise into a piece of 
plywood. Is that commonly done?

A couple people suggested that a 6" f/6 design would allow a lighter 
and more portable structure and give good performance. That is a 
tempting thought. I'm balancing two conflicting design preferences. 
Most of my observing tends to be high-magnification views of moons, 
planets and double stars from a very light-polluted location, so I'm 
not really shooting for a rich-field instrument. OTOH, most of my 
observing is in 1-hour evening sessions where the ability to grab the 
telescope and go out in the yard on short notice makes portability 
nice. From using the "Newt" design program, it looks like a 
reasonable obstruction size could be obtained in an f/6 instrument by 
using no bigger tube than necessary and a low-profile helical 
focuser.

Finally, everyone really seems to prefer wooden primary mirror mounts 
and I'm not sure why that is. A nice, open aluminum mount costs 
around $30-something which doesn't seem extravagent. For a 6" mirror 
is an aluminum mount like that less stable, durable or adjustable 
than a wood one? Or do most people just have more of a "I built it 
myself" desire than I do?

Thanks again for the replies. I'm ordering a copy of Berry's first 
book and also hope to contact one of the local club members with ATM 
experience for some mentoring. It's sounding more and more doable...