Solar/lunar transits

From: Matson, Robert (ROBERT.D.MATSON@saic.com)
Date: Fri Jan 26 2001 - 13:14:04 PST

  • Next message: Allen Thomson: "Re: Solar/lunar transits"

    Hi Bruno,
    
    > Even satellites in low earth orbit, which would be at a distance of 1000
    > to 2000 km from the observer, cannot be seen because the image would
    > be wiped out by atmospheric turbulence.
    
    Perhaps at 2000 km range, but at 1000 km a 10-meter
    object subtends 2 arcseconds.  This is within the
    realm of possibility.  And with a larger satellite like
    Mir, ISS or the Shuttle (where the range can also be
    quite a bit less than 1000 km), observation should be
    no problem at all.
    
    > In this respect, it is interesting to see photographs taken of Mercury
    > transits across the Sun. Such images have been published in SKY
    > & TELESCOPE on several occasions.
    
    I had no trouble seeing the most recent Mercury solar
    transit through 8 x 56 binoculars.  Granted, Mercury
    subtended 10 arcseconds, but with a modest telescope
    you could certainly get down to a couple arcseconds.
    
    > Perhaps, and I stress *perhaps*, it is possible to see such transits
    across
    > the moon. To my knowledge, no *verifiable* observation has ever been made.
    
    A sunlit transit of Mir across the lunar disk has been
    successfully observed.  I can dig up the rather excited
    report if you like.  Don't know if anyone has observed
    a silouette pass of Mir across the moon, however --
    perhaps that's what you're referring to.
    
    Cheers,
    Rob
    
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