Re: [ATM] [atm] how to test flat secondary mirror

["Philip Lardner" <philiplardner@eircom.net>]

Wiping it with my forearm? I haven't tried that yet... I've been too busy
trying every other method I could think of! Clean skin should contain just
enough oils to pick up all the dust. I'll give it a try. I have actually
just made a sheet of 'artificial skin' using a well laundered linen rag into
which I have melted a small amount of fresh bees wax. I am quite pleased
with the results so far, but I still have to wipe the plate several times to
cover all of its surface... my arm, being bigger and firmer, does it in one
sweep!

Thanks for the idea,

	Phil. 

-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
James Sturtevant
Sent: 29 September 2007 22:13
To: atm@atmlist.net
Subject: Re: [ATM] [atm] how to test flat secondary mirror

>The biggest problem I ran into was ensuring that the two plates under 
>test were totally free of dust. The tiniest spec of dust was skewing my 
>fringe patterns so much that I could never get two readings the same. I 
>haven't really cracked that problem yet, so if you have any ideas then let
me know!
>
>Hope this helps,
>
>	Phil.

    The traditional method is to wipe the surface with the underside of the
forearm or the hand. This works well, but only if your skin is very clean
and dry.

    I use the cleaning method that machinists use - compressed air. If you
aren't lucky enough to have a compressor in your workshop, try the cans of
compressed "air" that you can buy at Wal-Mart or Staples.


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