Columnar sundial
OwnerWilliam L. Bohlayerinventor
Life of this patent
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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.
Claims19
A sundial comprising:
- a hollow support column having a transparent portion;
- a translucent projection screen movably mounted on the exterior surface of said support column, said screen carrying analemma scale means;
- and
- an opaque nodus plate covering the upper end of said support column, said nodus plate having a node aperture for projecting a pinhole image of sunlight through said transparent portion of said support column onto the interior surface of said projection screen.
Dependencies are inferred from the claim text.