Equatorial mount pointing

From: Moritz Heger (moritz.heger@gmx.li)
Date: Tue Apr 03 2001 - 12:43:58 PDT

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    The mathematics for equatorial mount pointing are this simple that not even
    a piece of paper is needed: To provide a minimal rotation about the
    declination axis the RA axis (normally pointing towards the Polar Star) has
    to stand perpendicular to the approximated plane described by the point of
    the satellite rising, the maximum elevation point, the point the satellite
    touches the horizon again and the observer in the center. Then mainly this
    RA axis has to be used to track the satellite, with little movement of the
    Declination axis. In practical speaking, the RA axis has to point into the
    opposite azimuth where the maximum elevation occurs, and it has to be
    elevated against the horizon to 90° minus the maximum elevation of the
    satellite pass. An example: A satellite has its maximum elevation at 72° and
    the corresponding azimuth is 227° (SW). Then the RA axis has to point
    towards an azimuth of 47° (NE) and an elevation of (90° - 72°) = 18°. A
    drive rate can't be given as the satellite's apparent velocity changes over
    the pass. This method is practiced by myself using a 70mm refractor
    telescope without any electronics (ISS and STS give some illusion of a not
    pointlike appearance).
    Moritz Heger
    48.7080°N 11.3994°E 370m WGS84
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