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    Re: Latitude by Lunar Distance
    From: Frank Reed CT
    Date: 2006 Nov 12, 00:21 EST
    Alex E wrote:
    "However, the most interesting question (on my point of view)
    is not discussed.
    I mean DOES THIS METHOD REALLY WORK IN PRACTICE ??
    (There is no doubt that it is theoretically sound).
    And what does it mean that is works.
    Can you determine your position with this method
    and ordinary sextant
    a) to within 1/2 of degree?
    b) to within 20 minutes or 1/4 of a degree?"
     
    Well, I guess it all depends on the meaning of that phrase "ordinary sextant". <g> Some very ordinary sextants have arc error that would make them unsuitable unless this arc error has been rather laboriously measured. Of course, one reasonable way to do that measurement is by shooting lunar distances. But many ordinary sextants (metal ones only) have insignificant arc error and are certainly capable of measuring angles again and again to a couple of tenths of a minute of arc, no doubt about it. I've done it. I've seen a bunch of people do it in Mystic. By the way, as I mentioned before in this topic, I'm a big believer in averaging four sights whenever you're trying to do lunars. And this was considered normal practice historically. That way, assuming no underlying bias, if I have a typical error of 0.2 minutes of arc in each observation, the final average angle will be accurate to 0.1 minutes of arc.
     
    And you wrote:
    "But my Lunar's results are poor, either because of the
    poor sight or for some other reasons, I don't know."
     
    It might be eyesight, but I'm betting on technique (and that sticky micrometer in your SNO-T sextant). We'll have to talk about technique again soon. Maybe I can write up my thoughts on the matter early next week.
     
    -FER
    42.0N 87.7W, or 41.4N 72.1W.
    www.HistoricalAtlas.com/lunars

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