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    Re: EBBCO/filters
    From: Mike L
    Date: 2007 Nov 21, 03:47 -0800

    Hi peter,
    
    I tried searching and couldn't find the posts.
    
    My concern with using two polarising filters is that the UV may behave
    differently and not be polarised, so although the optical light is
    diminished, the UV comes through just as before!
    
    One solution I'm considering is using solar filters for astronomy and
    I quote (http://www.greenwich-observatory.co.uk/acatalog/
    Solar_Filte.html): "BAADER AstroSolar film has become the natural
    first choice for white-light solar observation. It's optical qualities
    are excellent, enabling you to see high-resolution images with a
    natural colour."
    
    Only problem is that it doesn't say how much the light is attenuated
    and although it ought to be suitable, I've no way of checking out
    before hand.
    
    The other alternative I'm considering is buying some sheets of optical
    filters - unfortunately with no guarantee on UV transmission so only
    for lunar work (is there any significant UV in moonlight?).
    
    Mike
    
    On Nov 21, 8:10 am, "Peter Fogg"  wrote:
    > Greg R
    >
    > Check out the List archives for discussion on using polarising filters. If
    > you use two in series they can be rotated for increasing combined density,
    > right up to total.
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