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Re: [ATM] Virtual Counterweights
Howard,
This is a great scope and is helping me formalize a few design elements. I
will study your document a bit more to come up with specific questions.
BTW, I just finished cutting my OTA and...IT IS ALIVE!
I am very excited to take this scope from the design phase to building.
Jack
-----Original Message-----
From: Howard Banich [mailto:hbanich@gmail.com]
Sent: Tuesday, October 24, 2006 1:15 PM
To: Jack Swaton @ Starry Host
Subject: Re: [ATM] Virtual Counterweights
Hi Jack,
I've made a small Dob that has the focuser at the center of rotation of the
altitude axis and found that the front end counterweight doesn't have to be
all that long: ( <http://hbanich.googlepages.com/TheSpringsonian.pdf>
http://hbanich.googlepages.com/TheSpringsonian.pdf)
I totally understand your concern about smacking someone with the
counterweight, but then this is really no more, and sometimes much less than
how far a long focus scope sticks out from its mount. In practice I've had
no problems like this, plus the counterweight idea easy to implement.
Howard
Portland, Oregon
On 10/24/06, Jack Swaton @ Starry Host <jswaton@starryhost.com> wrote:
Hmmm...good point on the center of gravity being over the center of the
tripod column. If I make the pier stiff enough then perhaps I can just place
heavy bags on the feet of the tripod. I'm just concerned about the
Springfield style bar sticking out in space ready to whack the unsuspecting
bystander. :-)
Jack
-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
Ross Sackett
Sent: Tuesday, October 24, 2006 4:18 AM
To: atm@atmlist.net
Subject: Re: [ATM] Virtual Counterweights
--- "Jack Swaton @ Starry Host" ...
> I'm now looking for ideas for virtual
> counterweights. The mount will have
> the altitude axis at the eyepiece so the eyepiece
> remains at a constant
> height to save my aching back.
Hmm, sounds like a worthy goal but I am a little
concerned that using spring counterweights rather than
the real thing will throw the whole scope off balance
on the short tripod. You are going to have to keep
the center of gravity of the whole setup over the
triangle made by the three feet, preferable close to
the center. I think that could be difficult without a
large top-end weight on a stalk, like the old
Springfield mounting.
Most spring counterweight systems are used to
compensate for small misplacements of the altitude
axis, usually on the order of an inch of less; in your
case you are using it adjust for an altitude axis that
is feet from the balance point. Not that you can't do
that in principle, but it seems to me that you might
be borrowing trouble.
Ross
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