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    Re: Towards a basis for Bruce Stark's Tables
    From: Fred Hebard
    Date: 2003 Jan 3, 15:48 -0500

    John,
    
    With the Davis Mark 3, I was using an artificial horizon, mostly a
    mirror, to shoot stars and planets.  I got so I was consistently
    within about 8 miles.  I determined, mostly with the Davis, but
    confirmed with the Husun, that inaccurate leveling of the mirror was
    the main culprit for the errors, by comparison to water or oil.  I
    was shooting at night from my deck and going inside between shots, so
    thermal effects were minimal: the index error of the Davis was fairly
    stable, and I got pretty good at checking and zeroing it out.  The
    lack of a telescope on the Davis Mark 3 is a disadvantage, as is the
    half mirror, half plain view, so that you never see overlapping
    images coming smoothly together.  A micrometer is also a necessity
    for precise movement of the index.
    
    Recently, I have been using a blackened pie pan with vegetable oil,
    which is less noxious than motor oil.  You don't want the oil so thin
    that surface tension distorts the surface, but it needn't be too
    thick, and needn't be colored dark.
    
    I expect the errors in my early shots were due to poor technique.
    
    Happy New Year!
    
    Fred
    
    --------------------------------------------------------------------------
    Frederick V. Hebard, PhD                      Email: mailto:Fred{at}acf.org
    Staff Pathologist, Meadowview Research Farms  Web: http://www.acf.org
    American Chestnut Foundation                  Phone: (276) 944-4631
    14005 Glenbrook Ave.                          Fax: (276) 944-0934
    Meadowview, VA 24361
    
    
    

       
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