Renaissance Focusing Sundial

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This is a new design in sundials developed by Precision Sundials LLC in Burlington, VT. Cylindrical focusing mirrors on the triangular support project a sharply focused beam on the inside of the helix. A timescale on the inside of the helix directly reads watch time to generally within 30 seconds of the atomic standard, when properly set up. The timescale slides in its helical track, allowing adjustment for daylight savings and the equation of time (seasonal variations in sundial time). The ball at the base has rotating wedges which allow for precise adjustment for setup at the user's latitude. The dial includes instruction for achieving exact alignment with the earth's axis, and has fine adjustments to assist this process. The helix is 27 inches across, and the focused sunlight travels once around the helix in 12 hours, at a rate of 6 inches per hour. Patent 6,301,793.

Here is a close-up of the focused beam of light. The width of the beam is 2 minutes of time, the same as the sun in the sky. Here the time is 11:55:30 Eastern Daylight (not solar) Time on September 30th. Each minute is individually marked and easily readable. The width of the beam is about 1/4 inch.
Here the dial shows12:57 (it reads right to left, because of the mirror), and the watch reads 12:57:23 (atomic clock time). This dial is generally accurate to better than 60 seconds all day long, due in part to "SundialAlign!" (see home page), the software used to achieve superior alignment with the celestial north pole.
This is a cutaway of the helix, showing how the moveable naval brass inner time scale glides on teflon runners to allow adjustment for the equation of time and Daylight Savings (see below).

This is the equation of time graphic located near the bottom of the helix. Aligning the date (here December 4th or September 30th) with the vertical marks sets the dial for Daylight Savings Time. Another set of marks one hour away allows the dial to be set for Standard Time.

Latitude is set by an initial one time adjustment of these wedges. A latitude scale hidden on the inside of the globe is calibrated from 23 to 51 degrees north. An unusual feature of these wedges is that no matter how they are adjusted, the sphere remains round.
Side View
Dial is about 44 inches tall.

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