Columnar sundial

Details Columnar sundial Columnar sundial

1981-08-24

1983-05-24

Martin, Jr., William D.

Geometrical instruments

Straight-line light ray type

Celestial

G04B 4904

Patent

active

043844081

ABSTRACT:
A columnar sundial utilizing the projection of the spot image of the sun through a nodus plate onto a translucent projection screen is disclosed. The projection screen is mounted on a support column which has a transparent portion through which the spot image is projected, with the nodus plate closing the upper end of the column. The projection screen is movable on the column to permit adjustment for display of seasonal time and date markings, and the nodus plate is provided with a series of apertures, one of which is selectively uncovered in accordance with the latitude at which the sundial is used. The column preferably is cylindrical with an elliptical cross-section, but may be circular in cross-section, and may have a non-cylindrical shaped surface.

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patent: 4135357 (1979-01-01), Ashton
patent: 4255864 (1981-03-01), Glendinning

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