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    From: Alexandre Eremenko
    Date: 2007 Mar 07, 17:32 -0800

    Bill and Fred,
    Here I post some observations with my MkIXa bubble sextant.
    I will appreciate very much if someone who also practices
    bubble horizon observations will compare these data with his/her own.
    March 7, Sun alt.
    Without averager. Errors: 5.6, -0.6, -2.3 2.0, -1.4, -1.7, 0.6, -4.1,
    -1.7. Average error: -0.4, sigma=2.8.
    (Bill: this is a  good example of how averaging works:
    the individual results are so-so (as shown by the sigma)
    but the average is excellent).
    March 7, Venus alt, with averager. Error 2.6.
    Without, errors: -3.0, 1.2, -1.9, -3.1, Average error -1.7, sigma=2.
    Febr. 20 Moon alt, with averager. Error 3.7.
    Without averager, error -1.6.a
    Febr. 20 Venus alt, without averager,
    errors 0.9, 1.9, -1.0, 0.1, -0.8, average 0.22, sigma 1.2
    Febr. 20, Sun alt. with averager, error 0.3,
    Without averager: errors -3.5, -2.7, -3.4, -4.1, 0.0, -2.8.
    I will be very interested if someone compares these results
    with his/her own observations with bubble horizon.
    Especially interesting is to know the performance of Cassens-Plath
    bubble attachment. For its price (at Celestaire) one can have 10 or 15
    aircraft sextants from e-bay, and surely several of them will work:-)
    And the weight is probably comparable (if you cut off the averager,
    of course:-)
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