Re: [ATM] New web pages & WIRE SPIDERS

["matt" <electro_optic@bellsouth.net>]

-----Original Message-----
From: Mike Lockwood <melockwo@uiuc.edu>
To: atm@atmlist.net <atm@atmlist.net>
Date: Friday, September 16, 2005 1:56 PM
Subject: Re: [ATM] New web pages & WIRE SPIDERS


>Hi,
>
>matt wrote:
>> talking of Moonlite focusers, while they look great , I found they have a
>> disadvantage for the kind of stuff I'm doing sometimes. The focuser body
>> looks massive and one piece , but unfortunately it is not a closed
cylinder,
>> rather a horseshoe shape . When the drawtube is extended and there is
some
>> significant load hanging off its end (imaging stuff for example) , the
>> leverage it creates is enough to ever so slightly spread apart the
horseshoe
>> ends , allowing the draw tube to sag , leading to a far less reliable
>> focusing than  if it had been a closed cylinder. Fancy shape, nice
looking ,
>> but too much flex in my view (for imaging) .
>
>Hmmm..... I believe what is flexing is the drive rod that is connected
>to the focus knobs, not the aluminum body.  It would be much more
>prone to flexure than the body.
>
>Hang enough weight off a FeatherTouch far enough away from it (like a
>friend does with his heavy H-alpha filter, extension tube, diagonal
>and eyepiece) and it will flex too.  Been there, seen it done!
>
> Mike Lockwood
>

you're right, there is a certain load point at which any focuser would start
having problems.
The Moonlite is doing it at a lower load than other Crayfords . I did
actually put a dial indicator on it and measured at that time that the body
was actually flexing, but didn't keep any record of how much , so it's just
my recollection. Bottom line, if I wanted to design a Crayford like that,
I'd start with a closed shape . I must confess I have no idea of course why
the Moonlite is shaped the way it is, I am not more qualified to comment
than any other ATM out there, and I aesthetically like the shape.

best regards,
matt tudor


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