[Aavso-photometry] Re: Crud on filters

[Bill Goff]

I've begun to wonder if this is more of a preventative maintenance 
problem; a few times a year cleaning the filter with alcohol or 
something just to keep the crud from accumulating.

Bill

On Oct 12, 2005, at 5:41 AM, arne wrote:

> I'm going to be talking about this problem in the Friday paper session.
> Once the paper is given, we'll get it posted on the web as soon as
> possible.  The culprit is the BG39 glass that is used as a red blocker;
> it is hygroscopic and needs to be protected from the environment.
>   Once the damage has been done, the only way to restore the filter
> is to repolish.
> Arne
>
> Wclark3 at cs.com wrote:
>> I too am having a problem with crud on my Schuler B and V filters. 
>> About everything was tried, distilled water and soap, distilled 
>> water, isopropyl alcohol (91%), and chemically pure (C.P.) acetone. I 
>> used q tips and microfiber lens cleaning cloths.  The only thing that 
>> was accomplished was to smear the crud around the glass.  I think the 
>> crud is some sort of glue or filler. A small piece