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    Re: Precision of lunars
    From: Alexandre Eremenko
    Date: 2007 Apr 24, 13:17 -0700

    Dear Frank,
    
    > You're still not getting very good results, and you're content to believe,
    
    In fact I thought that the results I recently posted are "very good".
    I would be very interested in seeing any results which you use
    as comparison pool. Your own of of those "novices".
    
    Meanwhile I post my recent results, so that together with the previous
    recently posted we have a complete set of 1 month observations.
    I stress that this is a COMPLETE set, including good and bad
    observations.
    If I wanted to choose a "typical one", by any criterion
    (average, median, etc.) this typical one will have error less than
    0.2.
    There are all Lunars with SNO-T and 6x scope.
    April 20 Venus at 11d. Errors: 0.1, 0.1, -0.2, 0.15.
    April 20 Saturn at 57d. Errors: -0.1, 0.1, 0.0
    April 21 Venus at 21d. Errors: -0.3, -0.2, 0.1, -0.2, -0.1
    April 21 Pollux at 19d. Errors: 0.0, 0.2, 0.2, -0.1, 0.2
    April 21 Spica at 110d. Errors: 0.5, 0.5, 0.5
    Same again, AFTER reduction of the previous 3:
    April 21, Spica at 110d. Errors 0.2, 0.0.
    (Explanation: I DID NOT preset the sextant, I just found out that I
    was overshooting by 0.5. After that I adjusted by eye.
    The problem was that Moon was too bright in comparison with Spica
    at that time. And using 2 light filters did not help. So I really did
    not
    see Spica at the moment of tangency, being overshined by the Moon).
    So I took another star which looked the same as Spica in that
    conditions:
    April 21, Regulus at 56d. Errors 0.5.
    April 23, Venus at 46d: Errors: 0.1, 0.2, 0.2,-0.3,  0.1.
    
    > So we can certainly
    > "see" angular shifts smaller than 0.5 minutes of arc.
    
    Sometimes we can sometimes not. (See the examples above with Regulus
    and Spica. They were faint on the background of city lights.
    Moon in another direction was too bright.
    There were no proper filters to "extinguish the Moon". Two light
    filters
    were not enough, and through the other two "sun filters" the Moon was
    not visible.
    
    
    > What's your latest
    > theory  on the reasons you've been unable to do as well as you would like with
    > your  observations?
    
    I have no theory, except that I gained some experience.
    Experience of a very special kind: just how should a star and Moon
    look
    when they really touch. And this depends on the star, weather
    conditions
    and the scope used, and many other factors.
    That's why I call this experience. This cannot be explained or taught
    in one hour.
    
    That's why I am so curious to see the statistics of novices that can
    do better
    with an unfamiliar sextant.
    
    Alex.
    
    
    
    
    > -FER
    > 42.0N  87.7W, or 41.4N  72.1W.www.HistoricalAtlas.com/lunars
    >
    > ************************************** See what's free athttp://www.aol.com.
    
    
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