R: [APML] Vacuum Pump

["Marco Lorenzi" <lorenzi@libero.it>]

Dave, i would love to hear about the 16" Hyperbolical Newt either...
Marco Lorenzi

----- Original Message -----
From: <Aplanatic@aol.com>
To: <astro-photo@seds.org>
Sent: Tuesday, October 02, 2001 9:20 PM
Subject: Re: [APML] Vacuum Pump


> I've made a prototype 4X5 vacuum film back that uses lung power to make
the vacuum.  Briefly, the film back consists of a machined 3/16" thick
aluminum plate with 0.054" diameter holes, spaced 0.5" on center.  The back
of the plate has a manifold cover and an 1/8" diameter hose connector.  A
vacuum hose runs to a leak-tight "JB-welded" one pound coffee can.  One port
on the can goes to the vacuum back and the other port goes through a valve.
The valve is connected to a hose and then to the human powered pumping port
(mouth).
>
> The can acts as a vacuum reservoir, of course.  I pull a partial vacuum on
the system by sucking air out of the can and then I close the valve.  If the
film back is smooth and finely finished, air leaks into the system so slowly
that the vacuum will last many hours.
>
> I plan on using this simple method for a custom 16" Newtonian hyperbolic
astrograph with a 4" image circle.
>
> Dave Rowe
>
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