[Aavso-photometry] Re: Crud on filters

[Bill Goff]

Shawn
Ok, thanks, good information...

Bill


On Oct 17, 2005, at 7:11 PM, Shawn Dvorak wrote:

> Bill Goff wrote:
>
>> 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
>>>
>>
>>
>
> Bill,
>
> My filter is from Schuler, and is cemented into the cell so I didn't 
> have a choice.  The cerium oxide cleaned up nicely with warm water.  
> The crud was not very bad, and primarily near the center of the filter 
> so it was easier to get at.
>
> I've had a couple nights' photometry with the filter and it seems 
> fine, though I haven't checked the transformation coefficients yet.  
> The flat I made certainly looks a whole lot better after polishing.
>
> Shawn
>