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    Lunar Distances with Alex's SNO-T
    From: Frank Reed CT
    Date: 2006 Oct 31, 00:35 -0800

    Yesterday, October 29, a little before sunset here in Chicago, I did
    some lunar distance sights using Alex E.'s SNO-T sextant by the lake
    near Diversey Harbor. First I did a series of index correction sights
    off the Moon. Carefully aligning the Moon images pole-to-pole, my
    observations were (on arc, off arc):
    33.1, 31.7
    32.9, 31.3
    32.7, 31.4
    32.8, 31.2
    Subtracting and averaging, I settled on an index correction of -0.75
    minutes of arc.
    
    The Sun was peeking between buildings near the lakefront and rather low
    in the sky, so I had time for only three lunar distance sights as
    follows:
    GMT        LD
    22:21:00  89d 57.8'
    22:24:05  89d 58.8'
    22:26:26  89d 59.4'
    The last one looked a little unusual through the sextant since the Sun
    was half-eclipsed by one the apartment buildings. Air temperature was
    50F, reported pressure was 29.90in. Hg. Averaging the three
    observations and clearing the result, I find an error of about -0.1
    minutes of arc. That is, the observation was short by a tenth of a
    minute of arc.
    
    Generally, I like this sextant a lot. It's the first chance I've had to
    try out this design. The inverting telescope is a great help for lunars
    since it has good magnification, but it certainly takes a little
    getting used to. For anyone on the list who may be unfamiliar with the
    SNO-T, it is derived from the German Freiberger with little
    modification, if I understand correctly, and it was apparently the last
    production model for the Soviet Navy. The only flaw I find in it so
    far, which I think bothered Alex, too, is that the micrometer has a
    significant amount of static friction. It has to be nudged a bit to get
    it moving. As it happens, the way I shoot lunars (and recommend
    shooting lunars), this is not a real problem.
    
    -FER
    www.historicalatlas.com/lunars
    
    
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