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    Re: Mylar Film as Artificial Horizon Windows
    From: Richard M Pisko
    Date: 2011 Mar 16, 12:35 -0700

    The mylar (as I understand the construction) is not supposed to be  
    stretched tightly on the frame.  How well does a flapping pane prevent  
    waves on the water surface?  Mind you, our winds today are about 50 kph  
    and a non cast iron frame might take off to the east; but I was really  
    asking about moderate breezes.  I should set up a tripod, theodolite with  
    solar filters, pan and frame . . . but it's just above freezing and I'm  
    cherishing my comfort more and more these days.
    
    Thank you,
    
    Richard . . .
    
    On Tue, 15 Mar 2011 17:39:42 -0700, Robin Stuart  
     wrote:
    
    > The fogging that I mentioned in the post also happens with the plastic  
    > and glass windows supplied with the Davis artificial horizon but at a  
    > slower rate. I don’t it think would be advisable to apply anything  
    > (onion juice, saliva etc.) to the windows as this might affect its  
    > optical properties and hence the sextant altitude readings. It is  
    > probably better just to let the water equalize in temperature with the  
    > air before putting on the windows. (Of course this only works if the  
    > temperature is above freezing which it often wasn't around the time the  
    > observations were made). Alternatively one might substitute sump oil or  
    > mercury for the reflecting surface in which case fogging should not be a  
    > problem.
    
    
    -- 
    Richard . . .
    
    Using Opera since the"Dog" died
    
    
    
    

       
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