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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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