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    Re: Dip-meter again
    From: Alexandre Eremenko
    Date: 2012 Mar 29, 01:25 -0400

    > Many thanks for drawing attention to Shufell's paper,
    > which has much more of interest than just the dip meter, including the
    > use of sextant telescopes with very high (x16 or x20) magnification
    They mention some yacht from which they made these observations
    but I suppose the yacht was moored in the harbor:-)
    My moderate experience suggests that such telescopes cannot be used from a
    ship less than 10,000 tons in the ocean, even in good weather.
    > having 50 mm objectives with mirrors to match.
    This is for twilight sights. I've seen some 50mm telescopes on e-bay
    fitted to C Plaths and even to some very old (pre-SNO) Russian sextants.
    > used a 7x 30 monocular all the time,
    7x30 prizmatic I tried once, and found no advantages in comparison
    with 6x30 inverting. But the 6x30 inverting weights a small fraction
    of the prizmatic. To pay for the upright image with this weight makes
    no sense to me.
    > conditions than the x4 Galilean supplied with the sextant.
    Yes. And 6x30 SNO inverting seems much better to me than the standard
    sextant Galilean telescope in all cnditions.
    > I imagined that the dip meter would be based somehow on the Blish prism,
    It definitely has two prizms and one mirror.
    First I thought "what is the mirror for?" One can rotate one prizm, but
    now I think I understand why a mirror is needed.
    The picture in the last page of Shufeldt, in cubist style, is not very
    informative. And for the Russian one, I only have a picture from the
    outside. I can only conjecture what is inside.
    I have a slightly better picture of Shufeldt's dip-meter from outside.
    (Picture No 2 of his report). It seems more complicated than the
    Russian one.
    Today I scanned Russian-language Internet, and found that two N-5 were
    recently sold on some inner Russian analog of e-bay. No pictures. I
    registred for this
    "Russian e-bay" and will try to watch. If all Soviet ships were supplied
    with this, I hope I will find one sooner or later.
    > I should very much like to have a copy of the
    > Russian account of the meter.
    The Russian one has different shape. I will scan and post it tomorrow
    together with better exterior picture of the Shufeldt one.
    > As
    > my studies of Russian have not advanced
    I will translate the description.
    > This reads like a challenge that I may well take up
    It was intended as a challenge. I just tried to express it gently:-)
    Myself, I never did with my hands anything more complicated than a simple
    home repairs. Yes, besides this, I cleaned one old C. Plath:-)
    P.S. BTW, here is a Russian sextant called SNO-M-T.
    Very rare, I suppose. Looks like SNO-M, but somehow "tropicalized",
    whatever this means. http://www.maurnavy.com/
    Item 12 from the top, $248(sold).

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