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    Re: Cleaning arc of Vernier sextant.
    From: Henry Halboth
    Date: 2006 Oct 27, 23:45 -0400

    To all,
    Frank has asked how the sextant arc and vernier was polished with ashes.
    I know of no technical dissertation on the subject, but can state my
    experiences with the caveat that there well may be other ways - under the
    general heading "different ships, different long splices".
    Being a smoker in those days, I kept a little tin of cigarette/cIgar
    ashes. or fag-ash as George has so wonderfully said, carefully sorted
    through to insure no unburned or other contaminating residue - actually
    my recollection is that cigar ash formed the best and finest abrasive. To
    use, one simply touched a finger draped bit of fine cloth to the ash and
    ran it lightly over the arc until the desired luster was obtained. In the
    shipboard environment, the cloth was probably sufficiently damp for the
    ash to adhere, whereas, in a low humidity environment it would probably
    be appropriate to dampen the cloth a bit. This method of polishing a
    sextant arc is certainly not a figment of my imagination, although I
    cannot with certainty say whether I read it in some obscure publication
    of yesteryear or if it was passed to me by word of mouth.
    George has mentioned the difficulty in obtaining sufficient lighting to
    read-off the vernier of a sextant. There is no question but that accuracy
    in reading-off is significantly affected by the lighting employed. Not so
    much the actual light or its intensity, but rather the angle at which it
    strikes the vernier/arc interface. The light source, whether it be the
    sun or lamp, should be so positioned that the maximum intensity is
    directed along the index arm at right angles to the vernier/arc
    interface. In the daytime, this does not present much of a problem; all
    one need do is step out of the chart house and direct the sunlight
    appropriately - as a matter of fact, the frosted glass panel usually
    affixed to the index arm, just above the vernier, is for the purpose of
    diffusing that sunlight to dampen excessive reflection from the arc while
    reading through the magnifier. At night, or at twilight in taking star
    sights, one must of course use the chart table light or some other
    convenient source; again the light must be directed along the index arm
    and the sextant manipulated so as to obtain the maximum intensity at the
    interface. After a time, it all becomes second nature and no great
    problem. It may well be that at least some of the reticence to star
    sights or other night observation originated in lighting difficulties
    mentioned by George.
    On Thu, 26 Oct 2006 23:02:00 EDT FrankReedCT@aol.com writes:
    > Henry H you wrote:
    > "If the truth were to be known, the conventional wisdom of my day
    > was  to
    > leave the sextant alone, crud and all. The more encrusted a
    > sailor's
    > sextant might be, the more experienced he (no shes then) and
    > competent he
    > was thought to be. The cigarette/cigar ash polish was advanced  as
    > an
    > alternative for the fastidious to use. How times have changed!"
    > Can you  describe this process of polishing with ashes? I'm having a
    > hard
    > time picturing  it. Are you pouring ashes onto the arc and then
    > rubbing them with
    > your finger,  or do you rub the cigarette/cigar itself, ashen end
    > down, along
    > the  arc?
    > -FER
    > 42.0N  87.7W, or 41.4N  72.1W.
    > www.HistoricalAtlas.com/lunars
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