Determining az/el

From: Matson, Robert (
Date: Wed Aug 29 2001 - 12:47:50 PDT

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    Hi All,
    With regard to determining local (horizon) coordinates, Markus
    provides good instructions for determining azimuth (compass)
    directions, but I would add a caveat to the problem of
    estimating elevation angles.  He wrote:
    > A similar yet more "guessing" method works for determining the elevation.
    > It is surprisingly easy to point your hand, arm, binoculars or what else
    > you have to an elevation of 45, because (surprise surprise...) that's
    > halfway between 0 (horizon) and 90 (zenith), so it's very easy to guess
    > and check.
    This is where you can get into "trouble".  Contrary to what
    you might think, most people are very poor at determining
    the zenith location, and are even worse at estimating the
    elevation halfway between the horizon and zenith (45 degrees).
    Nearly everyone grossly underestimates the elevation, and
    points around 30 to 35 degrees above the horizon.  Now, if
    you tell them to point to 60 degrees above the horizon, the
    average person will point about 45 degrees up.
    The fist-at-arm's-length method is a bit more reliable.
    If you hold out your fist vertically in front of you, heal
    down and thumb on top (like you're holding a beer mug), your
    fist subtends roughly 10 degrees (from the outside edge of
    your pinky to the knuckle of your thumb).  So 30 degrees is
    "3 fists", for instance.
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    This archive was generated by hypermail 2b29 : Wed Aug 29 2001 - 12:51:17 PDT