Re: [ATM] Berry out of date?

[Mike Lockwood <melockwo@uiuc.edu>]

Hi,

I'm back from vacation.

DU wrote:
> I have access to a (first edition) copy of the classic "Build Your Own
> Telescope" by Berry.  I'm interested in building the 6" dob scope, but
> I'm wondering how out of date the book is.  For instance, he builds
> his own tube from 1/2" ply whereas some plans I've found online use a
> cardboard tube.  Also, the ATM FAQ says this: "His designs are
> generally heavy and don't necessarily follow best woodworking
> principles."  I'm not an expert woodworker (though my f-i-l is), but I
> know my way around a hammer--would it be better to go with another
> design or what?

In my opinion both the cardboard tube and plywood tube are out of date 
in terms of mainly THERMAL design, that is, letting the optics cool 
and providing an optical path free of air currents.

Lots of holes around the mirror (and maybe a fan or two) and some 
holes (or a fan) in the top of the tube will let the mirror get closer 
to ambient and will let warm air escape, reducing tube currents.

I find them heavy too.  I am a good woodworker and would build a more 
open tube out of 1/4" ply with some framing.  You could even get down 
to 1/8" ply.  Or just use the framing!  That's just a truss tube.

	Mike Lockwood

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