Why set the Sunquest sundial to latitude and longitude?


The latitude position of the Sunquest sundial allows it to parallel the earth’s polar axis.

To establish an accurate reading, the Sunquest sundial must be adjusted to the exact latitude and longitude of the location where it will be used.

Adjusting the latitude crescent enables the gnomon to be precisely parallel to the north-south polar axis of the earth, also placing the time-scale crescent parallel to the earth’s equator.

youtube latitude

Click on the image to watch the youtube video on sundials and latitude.

This youtube video by ScienceOnline explains why the latitude is important.


Time zones and 15-degree time zone meridians.

Adjusting the longitude on the time-scale crescent to account for the time difference between your location and the meridian for your time zone will allow the sundial to show the exact clock time within your time zone.  Because the earth rotates every 24 hours, and one complete rotation equates to 360 arc-degrees, the meridians for time zone are established at each 15 degrees from the prime meridian in Greenwitch, England.

For each degree of longitude that your specific location deviates east or west from your time zone meridian, the sun time of your location will be four minutes earlier or later than clock time.

When these adjustments are made, the Sunquest sundial will be an exact scale model of the earth as it rotates around the sun.