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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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