Polar Envelope Sundial

It was invented in 2019 by Fred Sawyer, President of the North American Sundial Society (NASS), and consists of a uniquely-shaped wide gnomon (the shadow-casting part) permanently attached to a circular base and surrounded by a moveable ring that is marked on the outside edge in easy to read hours and subdivided5-minute intervals.

The outer edge of the base and the inner edge of the ring are both marked with calendars (date scales). Once the sundial has been installed on a horizontal surface with the base aligned to true North (or in the souther hemisphere, toward the South cardinal point), it is ready for use. The sundial is adjusted daily by turning the ring to line up the calendar position for the current date with the corresponding position on the fixed base calendar. Then the gnomon shadow matches clock time throughout the day.

The photograph at top shows a sundial made for the city of Victoria in Canada. The calendar marks are lined up for a date in early May. The sundial shows that the photograph was taken at almost exactly 1:25 p.m. The 3D-printed version currently available from NASS is made from gray plastic. It is 160 mm in diameter (about 6¼ inches). The height depends on the latitude for which the dial is constructed; usually it will be about 75 mm (about 3 inches). Two rings are provided for places that use Daylight Saving Time; simply swap the rings to “Spring Forward, Fall Back.”NASS now offers this unusual dial to the public, and all profits will benefit NASS goals of education and fostering dailing projects and the art of gnomonics as a 501(3)c not for profit organization.

We can only produce this dial for latitudes greater than 40° N or 40° S. At lower latitudes, the concept is equally valid but it becomes impractical to 3D-print the complex gnomon. Instead, a wedge can be used to incline a 40° dial to work at a lower latitude. Should you wish to pursue this option, a suitable wedge will be included with your dial.

Please contact This email address is being protected from spambots. You need JavaScript enabled to view it. before sending an order for a Polar Envelope Sundial. This will allow us to verify that our version is suitable for your purposes and location, and to confirm some configuration details.