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    Re: Aldebaran occultation
    From: Alexandre Eremenko
    Date: 2017 Mar 7, 02:26 +0000

    Peter,
    
    You wrote:
    
    "I was a little unclear I think.  For your question about using an occulting 
    mask to observe bright stars near the Moon in antiquity:  I don't know if 
    they used that technique, but it seems to me they "should have.  A simple 
    circular aperture centered on the star would do the trick.  The observer 
    would have to gradually move the mask, or his eye, or both, but that's not 
    difficult since the movement is "so slow.  I'd like to try it during the next 
    good opportunity.
    
    Yes, I will try too. This idea occurred to me when I observed the occultation 
    on Saturday, but I was looking continuously through my
    binocular and was afraid to interrupt and miss it.
    
    And you wrote:
    
    "Since I was using a telescope, none of this applies directly to my 
    observation session; but I was having a similar problem that a different sort 
    of masking was helping with.  The star was approaching the "dark limb of the 
    Moon, which was lit only by earthshine (reflected light from the Earth), 
    making its contrast pretty low with the dark sky.  So the idea was to move 
    the bright part of the Moon outside of "the eyepiece field of view, using the 
    baffles of the telescope as a kind of crude mask.  That tones done stray 
    light from the bright portion of the Moon and allows the dark limb to be seen 
    more clearly as "the star gradually approaches it.
    
    I understand. In my case I could not see any of the dark part of the Moon, 
    even through binocular. But the Moonshine of the bright part was so bright
    that it obscured the star, when observed with the naked eye.
    
    Alex.
    
    

       
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