An electronic sundial apparatus which signals the passage of each hour by a chime, bell or other audible indication and which requires no external source of power other than the sun. Inner and outer concentric hemispheres with vertically extending apertures, specifically slits, configured so as to diverge at their uppermost ends and having a location, length and shape corresponding to the azimuths and distance between the maximum and minimum altitudes of the sun in the sky at each hour throughout the year at predetermined latitudes collimate the sunlight once each hour. The collimated sunlight is detected by a photoelectric cell coupled to a signaling circuit powered by a photovoltaic cell.

An equatorial sundial according to this invention includes a dial surface and an elongated, rod-like gnomon fixedly secured in operative relation thereto. The dial surface is generally semi-cylindrical and concave toward the sun. The circumferential portion of the surface is further formed in the shape of a partial helix. The gnomon lies on the axis of the dial surface such that the longitudinal extent of the surface is transverse of the gnomon at an obtuse angle thereto. In a given geographical location, the sundial is so oriented relative to the earth that the gnomon is parallel to the earth's axis of rotation. With a proper pitch of the helical form of the dial surface, the opposite end portions thereof are offset in a direction parallel to the axis of the gnomon so that neither shade the dial surface either in the morning or evening.

An equatorial sundial apparatus with an adjustable base assembly utilizing one or more concave cylindrical focusing mirrors. One of the benefits that is derived from this apparatus is the use of one or more concave cylindrical mirrors to project a focused beam of light onto a calibrated surface from which the time can be read. This sundial has the additional benefit of not suffering from blurring of the time indicator in a shadow or non-focused beam of light typical of other sundials. This sundial's focused light forms a sharply demarcated indicator from which time can be read to the minute. A further benefit of this apparatus is the ability to incorporate multiple concave cylindrical focusing mirrors to reduce the size of the visual field or screen where the time is read and to incorporate various shapes and designs for ornamental purposes without significant compromise of the sundials accuracy for telling time. An additional benefit of this apparatus is the ability to quickly, accurately and easily adjust the apparatus to the proper tilt upon setup according to the latitude where it will be located by means of an adjustable base assembly.

A heliochronometer (10) for providing accurate clock time readouts at any known latitude and longitude location on the earth including, a base (15) to effect precision orientation and level mounting and having an unpstanding post (40), a latitude member (45) adjustably angularly positionable relative to the post for selecting a particular latitude, a gnomon assembly (65) extending upwardly from the latitude member, a longitude correction member (75) adjustably pivotally mounted about the gnomon assembly for effecting a longitude correction, a time dial support (20) pivotally mounted about said gnomon assembly and having an arcuate time dial (150) on which the shadow of the gnomon assembly is projected, and assemblies (90, 130) interconnecting the longitude correction member and the time dial support for adjusting the angular position of the time dial for daylight savings time and the equation of time.

This invention represents an improvement to an equatorial sundial comprising an independent simultaneous single scale indication of both time and date as represented from a primary and secondary gnomon. This allows one unfamiliar with the physics of an equatorial sundial to with simple observation quickly assess both time and date as a singular measurement. The sundial displays conventional time measurement on a single scale transcribed on the equatorial ring from a primary gnomon aligned with the polar axis. The improvement includes a date scale transcribed on the primary gnomon that is cast a shadow from the secondary gnomon comprised of the upper equatorial ring. Since the sun maintains an essentially equivalent angle of declination throughout the day, the shadow cast by the upper equatorial ring (secondary gnomon) on the primary gnomon (containing the date scale) remains consistent in position and date can be observed at any time of the solar day.