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    Re: Easy Lunars in 1790
    From: Alexandre Eremenko
    Date: 2006 Apr 27, 21:16 -0400

    Ken,
    
    > I don't have those particular calculations
    > handy as they are at home
    
    So can you send them when you come home?
    I am not asking for any calculations, just the row data:
    DR coordinates, GMT and the distance, of YOUR observations
    not Thompson's.
    
    > So if Thompson had an almanac based on a better theory of the moon as well
    > as a calculator to clear his lunar more precisely, his longitude would
    > only have been off by 4"  ;-)
    
    Well, this could happen only by coincidence, you cannot measure
    angles with any sextant consistently wo a fraction of a second.
    
    > (the posts are in the archives) we found that his standard deviation was
    > 20' (in longitude) using the old almanacs and would have been 14' if he
    > had the JPL data, so not bad but not great.
    
    That is 0.5' in the distance.
    This looks more plausible than 4".
    This I can also do from land with my sextant, almanac and calculator
    in good weather.
    
    > that he got this sextant in 1792 and there was much rough travel in the
    > interim (perhaps 30,000 miles by canoe, horseback, dogsled, and foot).
    > There are instances in his journals where his canoe is overturned in
    > whitewater and the sextant has to be fished out downstream.
    
    If you carry it in a proper box, you are unlikely to bend the frame.
    It will go out of adjustment, of course, but probably such an
    experienced person as Thompson would check and adjust his sextant
    before every observation.
    
    Thanks a lot, I will study the data you sent me.
    But you wrote that you tried to repeat his observations,
    and I am very curious to see the comparison of your results
    with his results.
    
    Alex.
    
    
    

       
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