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    Re: horizon marks using a level
    From: Peter Monta
    Date: 2017 Jul 30, 00:38 -0700

    If you draw a line on a wall to serve as a surrogate horizon, the sextant must be at exactly the same height above the ground for every sight.

    Could use some sort of monument right at the observer's location, so fixing both the near and far points of the line.  This could be as elaborate as a pillar holding a mask with an aperture of about the same size as the horizon mirror---the user observes the horizon mark through the center of this aperture.  But it should be possible to improvise using some ad-hoc nearby fixed mark such as a post or brick or railing.  Characterize several for the various heights-of-observer to maximize comfort---no one likes to stoop.

    Best solution?  Collimator at the distant point with solar-powered Bluetooth-enabled LED illuminator.  When you want to observe, your phone can tell the device to turn on or off.  The solar cells eliminate the hassle of changing batteries, and the reticle would have enough range to paint a reasonable range of observer heights.  I would totally buy one of these.  (Actually several, distributed around the horizon.)

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