[Aavso-photometry] Re: Crud on filters

[Shawn Dvorak]

Richard Miles wrote:

> Bill Goff wrote:
>
>> 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.
>>
>
> I tend to agree Bill.  Although the BG39 filter glass effloresces 
> (that's the chemical term) in humid atmospheres, it does not seem to 
> change the colour of the glass when inspected visually.
>
> So like you say, keeping it polished may be a good strategy but watch 
> what you use as the glass is quite soft - tin oxide is probably less 
> hard than alumina or rouge.  A soft lint cloth may be the best option.
>
> The white surface layer might be soluble in a very weak acid such as 
> lemon juice - I'll give it a try and let you know.
>
> Richard
>
>
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I cleaned the relatively mild crud off of my V filter today using cerium 
oxide using my finger and moderate pressure.  A few minutes' polishing 
completely removed the crud and left the filter looking as good as new.  
I'll hopefully get to try it out this evening if the clouds don't 
continue to thicken.

Shawn