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    Re: Lunar Exercise
    From: Frank Reed
    Date: 2008 Sep 23, 22:24 -0400

    JCA, you wrote:
    "Average the lunars and find UTC."
    
    My average LD was 71d 05.3' and with a DR lon of 75d 52.1' and the stated
    temperature and pressure, I find a "best" value of GMT of about 15:43:10
    give or take six seconds. Since Wilkes-Barre is up in the hills, it may be a
    good idea to reduce the stated pressure by perhaps 1 to 1.5 inches Hg. By my
    rough estimate, that shifts the best fit GMT ahead about ten seconds. That's
    not inconsistent with your estimate of an average time around 15:45 but
    without a real time check, there's no way to go beyond this step.
    
    The apparent lunar distance at that time and location was decreasing at a
    rate of about 0.45 minutes of arc per minute of time. Assuming you were
    taking sights at a rate of just about one per minute, the latter six out of
    your ten sights are fairly consistent and have a standard deviation error
    (relative to that calculated rate of decrease) of only about 0.35 minutes of
    arc. Under good conditions, as I have said in earlier posts, I get a
    standard deviation on individual lunar distance sights only slightly better
    than that (about 0.25' using a 7x scope). So is there any possible
    justification for dropping the first four out of ten of your sights? That
    depends... Were you "warming up"? I frequently drop the first one or two if
    I have enough sights (I don't even record them) and treat them as practice
    shots. On the other hand, you may have already taken a couple of practice
    shots which you didn't record... If we keep all of the sights, then the s.d.
    is more than doubled, to 0.76 minutes of arc, which is not so good.
    
    What was the magnification of your scope, by the way?
    
     -FER
    
    
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