[Aavso-photometry] Re: Crud on filters

[Bill Goff]

Shawn,
Interesting.  Are yours mounted and if so, did you unmount them for 
this cleanup?

Bill

On Oct 15, 2005, at 3:34 PM, Shawn Dvorak wrote:

>>
>> 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
>>
>>
> 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
>