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    Re: transit of venus 1769
    From: Frank Reed
    Date: 2006 May 27, 21:33 -0500

    C.A. you wrote:
    "Also Nevil Maskelyne began  printing an almanac in 1767 along with lunar
    tables in 1767, so the precise  value of the AU was not required to compile
    fairly accurate  ephemerides at  that time. "

    Yep. Even if the solar parallax had been wrong by 50%, it  would have had no
    significant effect on practical navigation. Such a large solar  parallax error
    would produce an error no greater than about 450 feet in a noon  latitude
    calculation (or any other line of position). The error in the longitude  deduced
    from a lunar distance observation using such an incorrect value of the  solar
    parallax would never be greater than about 2.5 miles. And of course the  real
    uncertainty in the solar parallax was closer to 10% in that era, so divide 
    those maximum errors by five.

    Since you're reading about Cook and  parallax, you might get a kick out of a
    BBC radio program which I posted about a  while ago. Here's the  link:
    You  can listen to it online or download it. It's fairly light and there's
    nothing  profound in it, but I enjoyed listening to it while driving through
    Pennsylvania  recently.

    I would also recommend Patrick O'Brian's biography of Joseph  Banks. Banks
    was the leader of the team's botanical contingent, and he was later  President
    of the Royal Society. Banks became an important figure on the Board of 
    Longitude, and he was a big advocate of the movement to colonize Australia with 
    convicts. It's interesting to note that Joseph Banks was the "media hero" of 
    Cook's transit of Venus expedition when they returned to England while Cook was 
    counted as little more than a bus driver. That perception soon  changed...

    And you wrote:
    "To respond to Frank Reed,  I seem to  recall that the transit was not
    visible from  my location near Los Angeles,  California but I cannot swear to it. 
    Dont know it the next transit will be  visible from here either. "

    You're right. The 2004 transit was not  visible in California. In
    Connecticut, we had to be up at sunrise to see just  the second half of it. If you're
    still in LA in 2012, you'll have good seats.  You'll see the beginning of the
    transit clearly, and you'll see the Sun setting  over the Pacific with Venus
    still in transit. That should make an impressive  sight.


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