Abstract: A method of determining solar radiation exposure at a predetermined location is provided. The method may include generating a first two-dimensional (2D) matrix including a plurality of elements, wherein each element of the plurality of elements of the first 2D matrix includes an elevation/azimuth pair representing a light ray extending from the predetermined location to one or more positions in the sky. The method may further include generating a second 2D matrix including a plurality of elements, wherein each index of the second 2D matrix includes an associated elevation/azimuth pair of the first 2D matrix. Each element of the plurality of elements of the second 2D matrix represents an amount of solar radiation to impinge on the predetermined location from a direction of a respective elevation/azimuth pair.

Abstract: A celestial instrument as a memorial sun dial or star clock has a flat plate body or a spherical body that includes two hemispheres facing one another and spaced apart by a circular gap allowing sunlight to pass through the gap in the instrument. A planar date ring containing graphics surrounds the flat plate or the sphere. Upper and lower gnomons are rotatably secured to the plate or to the hemispheres. A stand includes a holder for a latitude arm that supports the gnomons. When the gap is placed in alignment with the ecliptic, sunlight can pass through a gap parallel to the plate or through a lens within the spherical body focusing a spot of light onto a display surface. A pointer on a rotatable shadow arm indicates the time on a 24-hour clock face.

Abstract: The present invention relates to a timepiece comprising a frame and a device (1) for displaying the equation of time. The device (1) for displaying the equation of time comprises a first support (2) and a second support which are superposed, or, respectively, mounted so as to be able to rotate with respect to the frame, the first support (2) bearing a curve (6) that represents the equation of time, and the second support bearing a pointer (12) arranged such that the intersection of the pointer (12) with the curve (6) is visible, and means for driving the first (2) and second supports that are arranged such that the first (2) and second supports rotate at respective speeds that allow the value of the equation of time to be displayed at the intersection of the pointer (12) with the curve (6).

Abstract: A hemispheric armillary with arms and supporting a structure for supporting a gnomon over a time indicating dial plate is constructed to avoid the arms' shadows from eclipsing the gnomon shadow on the dial plate.

Abstract: Embodiments of a sundial. Various embodiments of the sundial disclosed herein may be used to determine the time of day based on the position of the sun. The sundial may comprise an at least substantially spherical curved reflector that may be at least partially transparent and at least partially reflective such that light from the sun can pass through a surface of the reflector and be reflected off of an internal surface of the reflector to reflect an image of the sun from the internal surface. The sundial may further comprise a dial face for viewing of a reflected image of the sun to provide at least an approximate indication of the time based on the position of the reflected image of the sun on the dial face.

Abstract: Embodiments of a sundial. Various embodiments of the sundial disclosed herein may be used to determine the time of day based on the position of the sun. The sundial may comprise an at least substantially spherical curved reflector that may be at least partially transparent and at least partially reflective such that light from the sun can pass through a surface of the reflector and be reflected off of an internal surface of the reflector to reflect an image of the sun from the internal surface. The sundial may further comprise a dial face for viewing of a reflected image of the sun to provide at least an approximate indication of the time based on the position of the reflected image of the sun on the dial face.

Abstract: Various embodiments of the sundials disclosed herein may be used to determine the time of day based on the position of the sun. The sundial may utilize a curved reflector to reflect the image of the sun onto a dial-face. The curved reflector may be disposed, at least in part, behind the dial-face. A portion of the curved reflector behind the dial-face may be used to reflect an image of the sun onto a back surface of the dial-face. The reflected image of the sun received on the back of the dial-face may, in some embodiments, be visible on the front surface of the dial-face. The dial-face may have a plurality of time markings positioned thereon. The position of the image of the sun on the dial-face may be compared to the plurality of time markings to determine at least an approximation of the time of day.

Abstract: A hemispheric armillary with arms and supporting a structure for supporting a gnomon over a time indicating dial plate is constructed to avoid the arms' shadows from eclipsing the gnomon shadow on the dial plate.

Abstract: A sundial for telling apparent solar time and clock time across a range of latitudes and longitudes. A solar dial is formed with an index point and a noon hour point. A plurality of concentric latitude indicia are centered at the index point and at least one map indicium is overlaid by the concentric latitude indicia where the map indicium has geographic latitudes corresponding with the concentric latitude indicia on the solar dial. The solar dial also includes a plurality of solar time indicia radiating generally outward from the index point drawn with respect to the noon hour point according to the hour line equation at each concentric latitude indicia intercept. An elongated gnomon projects from the index point, whereby the sun's shadow cast by the gnomon intersects the solar time indicia in relation to the concentric latitude indicia to provide a reading of apparent solar time for the user's location on the map indicium.

Abstract: A sundial for telling apparent solar time and clock time across a range of latitudes and longitudes. A solar dial is formed with an index point and a noon hour point. A plurality of concentric latitude indicia are centered at the index point and at least one map indicium is overlaid by the concentric latitude indicia where the map indicium has geographic latitudes corresponding with the concentric latitude indicia on the solar dial. The solar dial also includes a plurality of solar time indicia radiating generally outward from the index point drawn with respect to the noon hour point according to the hour line equation at each concentric latitude indicia intercept. An elongated gnomon projects from the index point, whereby the sun's shadow cast by the gnomon intersects the solar time indicia in relation to the concentric latitude indicia to provide a reading of apparent solar time for the user's location on the map indicium.

Abstract: A digital solar compass has a planar image sensor (5) for capturing an image of a gnomon (1) perpendicular to the plane of the image sensor. A cover (12) protects the gnomon and image sensor. A signal processor (14) is arranged to determine the angle of a shadow cast by the sun and the gnomon from the image captured by the planar image sensor. The gnomon (1) may be mounted directly on the planar image sensor (5) or the shadow may be formed on a diffuser sheet (3) and projected onto the image sensor (5) using a lens (4).

Abstract: Various embodiments of the sundials disclosed herein may be used to determine the time of day based on the position of the sun. The sundial may utilize a curved reflector to reflect the image of the sun onto a dial-face. The curved reflector may be disposed, at least in part, behind the dial-face. A portion of the curved reflector behind the dial-face may be used to reflect an image of the sun onto a back surface of the dial-face. The reflected image of the sun received on the back of the dial-face may, in some embodiments, be visible on the front surface of the dial-face. The dial-face may have a plurality of time markings positioned thereon. The position of the image of the sun on the dial-face may be compared to the plurality of time markings to determine at least an approximation of the time of day.

Abstract: Disclosed are embodiments of a sundial. Various embodiments of the sundial disclosed herein may be used to determine the time of day based on the position of the sun. The sundial may utilize a curved reflector to reflect the image of the sun onto a dial-face. The curved reflector may be disposed, at least in part, behind the dial-face. A portion of the curved reflector behind the dial-face may be used to reflect an image of the sun onto a back surface of the dial-face. The reflected image of the sun received on the back of the dial-face may, in some embodiments, be visible on the front surface of the dial-face. The dial-face may have a plurality of time markings positioned thereon. The position of the image of the sun on the dial-face may be compared to the plurality of time markings to determine at least an approximation of the time of day.

Abstract: Disclosed are embodiments of a sundial. Various embodiments of the sundial disclosed herein may be used to determine the time of day based on the position of the sun. The sundial may utilize a curved reflector to reflect the image of the sun onto a dial-face. The curved reflector may be disposed, at least in part, behind the dial-face. A portion of the curved reflector behind the dial-face may be used to reflect an image of the sun onto a back surface of the dial-face. The reflected image of the sun received on the back of the dial-face may, in some embodiments, be visible on the front surface of the dial-face. The dial-face may have a plurality of time markings positioned thereon. The position of the image of the sun on the dial-face may be compared to the plurality of time markings to determine at least an approximation of the time of day.

Abstract: An ultraviolet risk indicator instrument comprising a dial and a shadow projection device on it, the dial having colored areas that indicate different UV risks, defined by lines of declination (solstices and equinoxes) and solar hour lines calculated based on the transformation of the Hour Coordinates of the Sun (Hour Angle and Declination) in a 3D Cartesian Coordinate System, whose origin is the tip of the shadow projection device (being a polar style parallel to the rotation axis of the Earth, or a straight style perpendicular to the dial plane) using matrix calculations to produce the necessary rotations of the system, taking into account the latitude of the place, the declination and inclination of the dial. The style may be a rod or a triangular shape.

Abstract: Disclosed are embodiments of a sundial. Various embodiments of the sundial disclosed herein may be used to determine the time of day based on the position of the sun. The sundial may utilize a curved reflector to reflect the image of the sun onto a dial-face. The curved reflector may be disposed, at least in part, behind the dial-face. A portion of the curved reflector behind the dial-face may be used to reflect an image of the sun onto a back surface of the dial-face. The reflected image of the sun received on the back of the dial-face may, in some embodiments, be visible on the front surface of the dial-face. The dial-face may have a plurality of time markings positioned thereon. The position of the image of the sun on the dial-face may be compared to the plurality of time markings to determine at least an approximation of the time of day.

Abstract: Sundial apparatus with overlying barrier grid.

Abstract: Disclosed are embodiments of a sundial. Various embodiments of the sundial disclosed herein may be used to determine the time of day based on the position of the sun. The sundial may utilize a curved reflector to reflect the image of the sun onto a dial-face. The curved reflector may be disposed, at least in part, behind the dial-face. A portion of the curved reflector behind the dial-face may be used to reflect an image of the sun onto a back surface of the dial-face. The reflected image of the sun received on the back of the dial-face may, in some embodiments, be visible on the front surface of the dial-face. The dial-face may have a plurality of time markings positioned thereon. The position of the image of the sun on the dial-face may be compared to the plurality of time markings to determine at least an approximation of the time of day.

Abstract: A calendar indicating device can include easy placement through a north-south block (1) to orient an equinox line (3) to provide sunrise shadow indications of one or more solstice events such as the summer solstice or the winter solstice at the moment of sunrise. Designs can be based on remnants of artifacts that included some of the possible components, even for prehistoric man, in one integral stone device built from a stone base (2). Embodiments may include sunset indicator(s), solar altitude indicator(s), indicators for the maximum solar altitudes on the summer and/or winter solstice dates, and alignment aid(s).

Abstract: A calendar indicating device can include easy placement through a north-south block (1) to orient an equinox line (3) to provide sunrise shadow indications of one or more solstice events such as the summer solstice or the winter solstice at the moment of sunrise. Designs can be based on remnants of artifacts that included some of the possible components, even for prehistoric man, in one integral stone device built from a stone base (2). Embodiments may include sunset indicator(s), solar altitude indicator(s), indicators for the maximum solar altitudes on the summer and/or winter solstice dates, and alignment aid(s).

Abstract: The most accurate method of finding the true north is through astronomical observations, for example, by observing the position of the sun. However, the procedure is complicated. The instantaneous position of the sun must be calculated from astronomical data for each instance of observation, and the operator must wait for the predetermined time to come. Elaborate manual adjustments are required. The present invention discloses an automatic solar compass comprising a cylindrical omni-directional lens, a detection means, and a servomechanism. It is as easy to use as the magnetic compass, but much more accurate and reliable than the magnetic compass.

Abstract: A celestial navigation device. A full-featured embodiment is useful as a sundial and planisphere and for measuring, among other things, latitude, longitude, and for time to angle conversions. The device may have one or more rings and is based on a transparent circular tube having a gravity indicator, typically a ball or bubble, in the circular tube, which locates the lowest or highest point in the tube to indicate time or angle measurements against a corresponding scale. The device may have a 24-hour time scale, a calendar scale, and/or an angle scale. One embodiment includes a split analemma with separate north and south portions. Each analemma portion is used with a corresponding gnomon of a pair of gnomons, each on opposite sides of the tubular ring. A two-ring embodiment has an inner ring and outer ring rotatably slidable relative to one another. Two additional gnomons and star position marks may be provided for star sighting observations.

Abstract: Sundials and solar compasses including are disclosed. Some embodiments include an omni-directional lens, which can focus a sun beam into a sharp spot with a long depth of field. By projecting the spot onto a cylindrical panel, both the day of the year and the time of the day can be read off simultaneously with very high accuracy. Because of the simultaneous displaying of time and date, no equation-of-time correction is required. If the time is known, the true north can be determined with high accuracy, and the device becomes a reliable and easy-to-use solar compass.

Abstract: An apparatus receives a digital image of a sun trace chart having time gradient lines and a sun trace extent line for a site. A selector defines on a display points along the solar trace extent line to define a solar opportunity region. An adjuster adjusts the digital image based on the magnetic declination of the site. The solar exposure potential is determined based on the proportion of solar trace extent lines within solar opportunity region and potential solar exposure. Site adjustments to increase solar energy potential are facilitated. A method of evaluating a site for solar energy potential is disclosed. A solar exposure device for recording and analyzing a solar trace is disclosed.

Abstract: A measurement device comprising a horizontal track, at least one self-leveling foot coupled to the horizontal track, a hemispherical track coupled to the horizontal track, a movable sensor unit coupled to the hemispherical track, and a connector disposed on the hemispherical track for taking measurements on the ground.

Abstract: The most accurate method of finding the true north is through astronomical observations, for example, by observing the position of the sun. However, the procedure is complicated. The instantaneous position of the sun must be calculated from astronomical data for each instance of observation, and the operator must wait for the predetermined time to come. Elaborate manual adjustments are required. The present invention discloses an automatic solar compass comprising a cylindrical omni-directional lens, a detection means, and a servomechanism. It is as easy to use as the magnetic compass, but much more accurate and reliable than the magnetic compass.

Abstract: A horizontal sundial (1) that can be used to find standard time accurately and be manufactured on a commercial basis for any specific location, incorporating a gnomonic projection map (1M), a wire gnomon (1a) to indicate the time on a scale (1b), and the point of noon on the map (1c), and a bead (1d) located directly above the center of the dial for indicating the Sun's overhead position on the map (1e), and marking special occasions and special dates.

Abstract: A sun dial including a housing, a light detector mounted on the housing exposed to detect ambient light, a logic circuit mounted in the housing for processing the detected light for determining over a preselected period of time the average light detected by the light detector, and an indicator to indicate upon demand, the average light detected during the preselected period of time. A method for determining average light detected over a period of time by detecting light above a preselected threshold indicative of darkness, while noting the time of darkness, adjusting the period of time by subtracting the time of darkness from the period of time, calculating the average light detected over the adjusted period of time, and giving a visual indication of the average light detected.

Abstract: 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.

Abstract: An astronomical, particularly solar and/or lunar, goniometric indicator comprising a reflecting member (1; 16; 20) having at least one planar surface scored with substantially circular and concentric microgrooves, wherein the width and the depth of each microgroove and the distance between adjacent microgrooves are adapted to let a diametral line of diffracted and/or reflected light appear when the at least one planar surface is illuminated by a light source, the reflecting member (1; 16; 20) having at least one orientation line (2, 17) that is radial with respect to the microgrooves.

Abstract: A vertical sundial comprises a substantially flat dial face (2) provided with dial markings and gnomon (3) supported in a fixed position relative to the dial face (2) which in use casts a shadow on a first side of the dial face (2). The sundial is adapted to be free-standing on a generally flat and horizontal surface and the dial face (2) is translucent such that the shadow cast by a gnomon on the first side of the dial face can be observed from the second side of the dial face. The dial markings are adapted to be read from the second side of the dial face to give a time indication.

Abstract: An astronomical, particularly solar and/or lunar, goniometric indicator comprising a reflecting member (1; 16; 20) having at least one planar surface scored with substantially circular and concentric microgrooves, wherein the width and the depth of each microgroove and the distance between adjacent microgrooves are adapted to let a diametral line of diffracted and/or reflected light appear when said at least one planar surface is illuminated by a light source, said reflecting member (1; 16; 20) having at least one orientation line (2, 17) that is radial with respect to said microgrooves.

Abstract: A solar counter to provide an accurate way of measuring the middle of the night or another selected fraction of the day or night. The solar counter activates an electronic event when it has finished counting down. For example, a lamp can be turned off half way through the dark part of the night. This process is extremely accurate, and adaptations of this concept can be used in the safety industry, irrigation, or in agriculture. One embodiment of this concept has a battery back-up circuit, but a substitute 50/60 Hz clock input frequency in the case of AC power loss can also be provided using an uninterruptible power supply (UPS).

Abstract: A mechanism for determining whether the sun is visible at a diurnal solar event and for mechanically triggering actions based upon the sun being visible during the diurnal solar event is disclosed. The mechanisms of the invention can perform these operations without intervention or supervision for long periods of time. Certain embodiments have been applied to provide a diurnal solar event trigger based upon sidereal noon for a clock providing accurate timing for 10,000 years without intervention or supervision.

Abstract: By adding an opaque ecliptic half-plane (24) to a partially open or transparent equatorial disk (12) which bears a sidereal hours scale (20), and by being able to rotate this plane (24) and disk (12) jointly in order to minimize the shadow being cast (74) by ecliptic half-plane (24), one can easily determine the local sidereal time using the sun. Understanding its operation draws on a number of basic concepts that a beginning astronomy student should master, and should also interest sundial enthusiasts.

Abstract: An apparatus for use with a source of light including a first orientation device that includes a latitude scale, a latitude pointer rotatable about a first axis relative to the latitude scale, and a platform configured to support an architectural model. The platform is mounted on the latitude pointer such that rotation of the pointer about the first axis produces a corresponding change in the position of the platform relative to the latitude scale. The apparatus also includes a second orientation device that includes a time scale and a time pointer rotatable about a second axis relative to the time scale. The first orientation device is mounted on the time pointer such that rotation of the time pointer about the second axis produces a corresponding change in the position of the platform relative to the time scale without changing the position of the platform relative to the latitude scale.

Abstract: An apparatus for use with a source of light including a first orientation device that includes a latitude scale, a latitude pointer rotatable about a first axis relative to the latitude scale, and a platform configured to support an architectural model. The platform is mounted on the latitude pointer such that rotation of the pointer about the first axis produces a corresponding change in the position of the platform relative to the latitude scale. The apparatus also includes a second orientation device that includes a time scale and a time pointer rotatable about a second axis relative to the time scale. The first orientation device is mounted on the time pointer such that rotation of the time pointer about the second axis produces a corresponding change in the position of the platform relative to the time scale without changing the position of the platform relative to the latitude scale.

Abstract: A sundial for indicating the time of day using the position of the sun having a labyrinthine body with a plurality of pathways connecting a first and said second face, each pathway being adapted either to transmit said ray of light from an entry end at the first face to an exit end at the second face or to absorb said ray of light depending on the solar position so that the second face indicates visibly the time of day.

Abstract: A horizontal sundial constructed to accurately tell time at a specific latitude having female threads incorporated into both the north (10) and south (12) sides of the dial plate (6). Threadedly matched male gnomon angle-adjusting bolts (18) serve to raise either the north or the south end of the dial plate and gnomon. This serves to bring the gnomon to the same angle with the horizontal as the latitude of intended use. The female threads (10) & (12) can be located on the face of the dial plate (6) to establish a simple mathematical relationship, such that a one degree change in gnomon elevation will correspond to a whole number of revolutions of the gnomon angle-adjusting bolts (18).

Abstract: 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.

Abstract: An antenna for receiving a satellite broadcast can adjust orientation at higher precision than a method based on a compass and a level, without being influenced by environmental magnetic field generated by magnetic body or electromagnetic sources, can perform adjustment of orientation even before a radio wave from the satellite is not catched, can monitor the deviation during the fixation of the antenna orientation to improve the workability in adjustment of antenna orientation. The antenna for receiving a satellite broadcast has a reflector for reflecting a radio wave from a satellite on a reflecting surface for convergence and a receiving portion for receiving the radio wave reflected by the reflector. The antenna further includes a light blocking portion forming a shadow by the sun light, a scale determining a direction of the sun by the shadow formed by the light blocking portion. The light blocking portion and the scale are provided at an upper end portion of the reflector.

Abstract: The present invention is a sundial having first and second spaced parallel planar projection surfaces, the first projection surface defining a summer projection surface and the second projection surface defining a winter projection surface. A gnomon extends perpendicularly between the summer and winter projection surfaces. The gnomon is positioned relative to the summer and winter projection surfaces so that with the sundial in an operative alignment with the parallel projection surfaces parallel to the equatorial plane of the earth, on sunny days a shadow is cast by the gnomon on the summer projection surface during those days when the sun rises above the equatorial plane in the northern hemisphere and a shadow is cast by the gnomon on the winter projection surface during those days when the sun does not rise above the equatorial plane in the northern hemisphere.

Abstract: A satellite antenna alignment device is described for use with a satellite antenna to enable the satellite antenna to be aligned with respect to a particular satellite. The alignment device is operatively secured to the support arm of the satellite antenna and includes a compass for indicating the directional position of the support arm and also includes a clinometer.

Abstract: A holographic sundial comprising a hologram made using a holographic recording apparatus including a light-sensitive recording medium, a three-dimensional model, in one or more parts, bearing a plurality of indicia over a range of angles corresponding to hour angles of the sun, illumination of the three-dimensional model such that light is incident on the light-sensitive recording medium from every angle of the three-dimensional model in a manner conformal to the represented hour angle, and a reference ray of light incident on the recording medium from one angular direction which defines the angular direction for viewing the recorded image. The hologram, under direct illumination by light from the sun, produces a continuously varying image which indicates the time of day.

Abstract: A sundial gnomon including a first surface having a plurality of parallel first surface apertures transmissive to light and through which a plurality of sunbeams pass, and a second surface having a plurality of second surface segment apertures for regulating the passage of sunbeams passing through the plurality of first surface apertures. The plurality of second surface segment apertures are arranged in a plurality of stencil patterns, each stencil pattern including a plurality of second surface segment apertures. The plurality of second surface segment apertures are configured to cause sunbeams passing through the plurality of first surface apertures to be incident upon second surface segment apertures of only one stencil pattern at a given time. Thus, sunbeams passing through the two surfaces will display the hour of the day. Preferably, the gnomon includes a second set of surfaces having apertures therein through which sunbeams pass to respectively display portions of an hour such as 10 minute intervals.

Abstract: A digital sundial displays the current solar time in digits, words, or pictures. Two closely-spaced parallel masks project different images depending on the angular position of the sun in the following way: The first mask, a regular array of thin vertical slits, casts a striped light pattern onto the second mask. This light pattern is independent of the height of the sun. The second mask is composed of narrow stripes of the digits, words, or pictures to be displayed. The striped pattern of sunlight cast by the first mask illuminates exactly those stripes of the second mask corresponding to the image representing the current time. The light shining through both masks is projected onto a translucent viewing screen mounted closely behind the second mask, which results in a digital display of the time. A plate of light-refracting material can be inserted between the two masks, effectively linearizing the motion of the light pattern cast onto the second mask.

Abstract: A direction indicator includes a base defining four edges that extend parallel to a horizontal surface on which the base is placed and form portions of respective sides of a rectangle, a bearing indicator which is selectively positionable on the base for carrying compass bearing information, and a gnomon supported in a predetermined position relative to the direction indicator. The bearing indicator may further contain time markings in the event that it is used as a sundial. The base is adapted to be placed in a predetermined orientation on a horizontal surface. For a given orientation of the base, the direction indicator can be appropriately positioned relative to the base by reference to the direction of a shadow cast by the gnomon at a predetermined time of day and by reference to the bearing of the sun at that predetermined time of day.

Abstract: A universal sun-clock is described comprising a base, on whose surface there are present a sun-dial (consisting of a clock-face and a time-pointing tongue) and a reference mark for orienting the sun-clock according to the longitude and an upright (hinged to an end of a support which can be drawn out from the base) bearing a semicircular sector, free to rotate around a pin, on which sector a latitude scale (graduated from 90.degree. of latitude North to 90.degree. of latitude South) is marked: an index integral with the upright allows to read the latitude on the semicircular sector. When the sun-clock is in a working position the support is drawn out from the base and the upright is rotated around its hinge until it is perpendicular to the base, whereas when the sun-clock is in a rest position, the support is retracted into the base and the upright, by rotating round its hinge, is pulled down onto the base.

Abstract: A sundial is described using a mirror to reflect an indexing spot of sunlight onto the back of a translucent dial face that is marked with time and date indicia. Adjustments are provided so that a sundial designed for any location can be used in another location and still provide accurate zone time and date.

Abstract: A sundial including a strip-shaped body with surfaces substantially in the form of helicoids. The body is made of a rather thin material. At least one of the helicoids is provided with time markings. As a result, the sundial is very simple to manufacture, and it is very easy to set up. Moreover, it is very easy to read the time, even at a relatively long distance.