Re: [APML] Dry Air Purge Rate for hypered film?

[Philip Perkins <philip@astrocruise.com>]

I have been using two nitrogen cylinders alternately - both about 16 - 18 
in tall.  They each provide enough gas to last a year and can easily be 
lifted by one hand.

If dry air works then by all means do it, but as Kent pointed out, oxygen 
needs to be removed too for optimum results.  Some of the answers depend on 
perspective, but if I was doing dry air purge I would worry that results 
would not be optimum, even though it may "work".  Is doing N2 purge 
"hard"?  Maybe doing astrophotography is even harder!  But actually it's 
not hard - N2 gas is easy to find anywhere and small cylinders are quite 
cheap.  The regulator, flowmeter and needle valve are standard parts from 
any gas supply company.  N2 purge may work better for remote operation 
because no power is needed to drive anything.

The only part that I found hard was deciding how to drill the camera (the 
nervousness made it hard!) but some form of gas inlet needs to be provided 
whatever purge method is used.  This is an article I wrote many moons ago 
showing the various bits, how I drilled the camera, 
etc:  http://www.astrocruise.com/gaspurge.htm
--Philip
Philip Perkins - philip@astrocruise.com
Wiltshire UK & Luberon France
Astrocruise - http://www.astrocruise.com

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