Re: [ATM] A little scope for my Dad :)

["Andreas Derwahl" <andreas@duda-derwahl.de>]

Hi James,

I had a look at your "Dadscope" and must confess that I've never seen
anything quite like it before. It certainly is a unique telescope (and with
unique colors, too :-) ).

What matarial combination do you use for the altitude bearings? It looks a
bit like steel to plastic, right? I understand the recommended ratio of
mirror to bearing diameter is something like 1 : 1 / 1.3 (from
Kriege/Berry).
I guess you don't need alt bearings that big, since you can balance your
design very well, but how are you satisfied with the handling? Can you
adjust the drag on the alt bearings?

I am asking because I am currently building a 10" f4.9 travelscope (rough
design of the OTA can be seen here:
http://www.duda-derwahl/ATM/aluscope2.jpg) and want it to have a collapsible
rockerbox made from a plywood ring and aluminium tubes.

For static reasons one of the designs I was thinking off, is very similar to
yours, with maybe a slightly larger bearing which is covered with ebony star
formica on the side and a piece of springloaded teflon pushing against it
for adjustable drag. That way I could have the favourable near triangle
arrangement of your rockerbox, and still finetune the altitude drag to match
the azimuth drag for optimum performance.

I know, it is a difficult question to answer, but from your experience, do
you think this could work in principle? Has anyone ever done a design like
this?


Certainly your rockerbox looks like it could easily take a much heavier
scope, very solid.

Thanks for sharing,

Andreas Derwahl


----- Original Message ----- 
From: "James Lerch" <jlerch1@tampabay.rr.com>
To: <atm_free@yahoogroups.com>; "ATM" <atm@atmlist.net>
Sent: Sunday, January 09, 2005 7:29 PM
Subject: [ATM] A little scope for my Dad :)


> Greetings All,
>
> Here's some pictures of a mostly powder coated aluminum scope I built for
my
> Father as a Christmas / Birthday / Father's day type gift :)
>
> http://lerch.no-ip.com/atm/Projects/Dad_Scope/page_01.htm
>
> Only two problems with the design:
>
> #1 It uses a ridicules amount of stainless fasteners to attach the 1/4
birch
> plywood panels the to the aluminum framing
>
> #2 (the biggie)  The altitude bearing are attached to the 1/4" thick
plywood
> filler panels.  This produces a noticeable amount of oscillations in the
"bump
> test".  When I can pry the scope out of my Father's hands, I'll add some
> additional framing to help support the altitude bearings..
>
>
> Take Care,
> James Lerch
> http://lerch.no-ip.com/atm (My telescope construction,testing, and coating
site)
>
> "Anything that can happen, will happen" -Stephen Pollock from:
> "Particle Physics for Non-Physicists: A Tour of the Microcosmos"
>
> " Press on: nothing in the world can take the place of perseverance.
> Talent will not; nothing is more common than unsuccessful men with talent.
> Genius will not; unrewarded genius is almost a proverb.
> Education will not; the world is full of educated derelicts.
> Persistence and determination alone are omnipotent. "
>                                                            Calvin Coolidge
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
>


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