Date: Wed, 15 Mar 2006 10:54:08 -0500
From: Shawn Dvorak <sdvorak
To: Roland Roberts <roland
References: <002f01c647c5$87b0d400$0200a8c0
	<m2veuflr6o.fsf
	main.rollinghillsobs.org
	version=3.0.4

Roland Roberts wrote:

>>>>>>"Shawn" == Shawn Dvorak <sdvorak
>>>>>>            
>>>>>>
>
>    Shawn> I use the Astrodon/Schuler V filter and see pretty severe
>    Shawn> deterioration over a single season.  Of course, the Florida
>    Shawn> climate is undoubtedly a tad hard on the filter, though I
>    Shawn> have started shuttering the observatory during the warm,
>    Shawn> rainy summer months, bringing the equipment into the air
>    Shawn> conditioned house so it no longer has to suffer the worst of
>    Shawn> the weather.  I've not actually replaced the filter over the
>    Shawn> past two years, however, since I've gotten satisfactory
>    Shawn> results by cleaning the deposits off with cerium oxide from
>    Shawn> an old mirror polishing kit.  A few minutes of cleaning with
>    Shawn> a bit of water and gentle pressure with a thumb/finger is
>    Shawn> sufficient to remove the whitish film.  Of course, over time
>    Shawn> the filter will end up some scratches, and perhaps the color
>    Shawn> balance will shift a bit as well, but I hope to get a few
>    Shawn> more years out of this inexpensive filter.
>
>and I'm trying to image what sort of deposits we're talking about.
>
>roland
>  
>
There was a recent thread on this, I think on this mail list, and also 
apparently some discussion at the last AAVSO meeting.  Basically, one of 
the glass layers in the filter composite is affected by moisture and 
develops a tough, thin film.  It's easiest to detect the film by looking 
even before the film is visible when just looking at the filter.  The 
is the best approach.  I don't know if anyone has done any analysis to 
see if there's any substantial color shift as the glass deteriorates.

Shawn
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