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This page introduces a unique instrument which uses a laser beam to simulate rays of sunlight. The purpose of the instrument is to lay out large and complicated sundials. The device was made out of a small transit. A transit has two axes of rotation which are aligned at right angles to each other. The Laser Trigon uses these two axes to control the direction of a laser beam so it can project sundial hour lines, as well as the lines and curves of the sun's declination, onto any surface, regardless of orientation or complexity.  Once in position, the Laser Trigon becomes a model of the celestial sphere as it relates to the position of the sun and the local site. The instrument is mounted so the 96 tooth index gear lies in the plane of the equator where it becomes an auxiliary equatorial dial. The 96 teeth provide the hour angles for 24 hours sub-divided into quarters. The laser is moved along the hour lines by sweeping the declination motion The declination index (the vertical motion of the original transit) is at right angles to the equatorial index, thus in position to control the laser for the lines and curves of declination. This index has three positions corresponding to the solstices and the equinoxes. When used to locate a declination, the equatorial motion is free to sweep from side to side. |
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This machine will project a sundial on any surface that sits still. |
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Below are three sketches of the Laser Trigon in position to draw a dial at latitude 40°. From left to right the declination index is shown in position to project the equinoxes, the winter solstice, and the summer solstice.  A more complete discussion of the Laser Trigon, including a description of its origins in traditional dialing tools can be found in Compendium 3-2 of the North American Sundial Society (June 1996). I recently built a large experimental sundial by using the Laser Trigon to project a dial on a rather unusual object. Visit the Shadow Garden, |
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Mr. Erich Polläne of Germany is offering for sale an instrument similar to the Laser Trigon. He calls the device the "Terrax-Laser", and his description follows.
The Terrax-Laser is a universal protractor for determining the deviation of a wall by means of the sun as well as constructing the division of a sundial using a laser beam to ease the work of sundial builders. A sliding scale with lens adapter allows adjusting the deviation of the zone time to the time zone meridian. Projecting the hour lines from the equatorial plane, determining the pointer length of the knot, graphs of the months, zodiac lines, equinox and solstices is possible by attaching the instrument to the gnomon. Correcting the gnomon may be achieved as well. For measuring a wall, the instrument is attached to a photo tripod with a 1/4" thread and a three point adjustment for leveling in the horizontal plane. Degree scales and a hole gnomon facility indicate noon and the equation of time and thus the direction of the wall. The device may be used as a leveling instrument as well. The instrument is built for a gnomon diameter of 12mm, that has to be mounted on a ball bearing. Mr Pollähne also manufactures a line of unique Optical Sundials. The price of the Terrax-Laser is 1250 DM. For more information, contact: Erich Pollähne MEKU GmbH Am Weingarten 14 30974 Wennigsen Germany |
Dialist's Notebook. 