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    Sextant mirror stability
    From: Fred Hebard
    Date: 2004 Oct 13, 23:31 -0400

    I haven't studied the following experimentally, but it seems to me that
    sextant mirrors take a while to "settle down" after they are removed
    for cleaning, etc.  It also seems better not to adjust them if there is
    no side error or failure of index mirror perpendicularity, as long as
    the index error is a reasonably small number, such as under one or two
    minutes of arc.  "The Sextant Handbook" also cautions against
    over-adjustment.  I wonder what other's feelings, experience, etc are
    about this.
    On Oct 13, 2004, at 8:08 PM, Alexandre Eremenko wrote:
    > Lisa:
    > On Thu, 14 Oct 2004, Lisa Fiene wrote:
    >> As I have interpreted it, the screw on the horizon mirror that is
    >> closest to the frame is for correcting Index Error, the screw which is
    >> furthest from the frame is for Side Error (shear).
    > I understood it in the same way.
    > So far, I don't know what my Index Error is, but know it is
    > small: all star tests show exact 0 or sometimes -0.1'.
    > But the Sun tests show -0.2' to -0.3'.
    > So I never touched this screw.
    >> Will look at the perpendicularity thread,
    >> although I did not find any
    >> difficulty with the adjustment of the index mirror.
    > Some of my messages earlier in this thread were
    > incorrect: having experience only with SNO-T I generalized it
    > to all sextants.
    > Alex.

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