Geometrical instruments – Straight-line light ray type – Celestial
Patent
1989-04-12
1990-05-15
Will, Thomas B.
Geometrical instruments
Straight-line light ray type
Celestial
33268, G04B 4902, G01C 1734, G01C 2102
Patent
active
049245929
ABSTRACT:
A typical plate and gnomon sundial with an enlarged dial plate and an extended gnomon is provided with latitude and longitude displacement indicia lines on the dial plate, beneath the gnomon and beyond the time indicia. A point is established on the gnomon from which a plumb line to the latitude and longitude displacement indicia lines can be determined. The latitude and longitude displacement indicia lines are placed so that when a plumb line from the point on the gnomon intersects the point of intersection of the site latitude indicium line with the site longitude displacement indicium line, the gnomon will be inclined to the horizontal at an angle equal to the latitude of the site and the plane(s) containing the gnomon and the 12 o'clock noon indicium line(s) will be inclined to a vertical plane containing the gnomon at an angle equal to the difference between the longitude of the site and the longitude of the time zone meridian.
Set up is accomplished at the site by plumbing from the point on the gnomon to the point of intersection of the site latitude and site longitude displacement indicia lines, and while holding this attitude rotating the sundial on a horizontal surface until the correct zone time is indicated by the shadow of the gnomon from the sun on the time indicia. This will mean that the sundial is correctly oriented and will continue to indicate correct zone time.
REFERENCES:
patent: 78133 (1868-05-01), Risch
patent: 2440827 (1948-05-01), Mareau
patent: 2441636 (1948-05-01), Kaufman et al.
patent: 2531932 (1950-11-01), Brown
patent: 4081911 (1978-04-01), Eldridge
patent: 4333243 (1982-06-01), McLaughlin
patent: 4835875 (1989-06-01), Fuller
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