Sundials - World's Oldest Clocks

North American Sundial Society

nass_news_2014_jun_WestminsterDial
Westminster Dial with Analemma Casting Mirror on Top
Photo Credit: Robert Clark

How do you get the people of your town interested in astronomy?  Robert (Bob) L. Clark a retired professor of mathematics and computer science and member of the Westminster Astronomical Society had the obvious answer: Build a unique sundial.

In the grassy field next to Hoffman’s Ice Cream in Westminster, the Westminster Astronomical Society dedicated a simple horizontal dial attached to a pole with a unique “ornament” … a vertical south facing mirror.

At the dedication on May 24th 2014 Jim Reynolds, director of the Bear Branch Nature Center Planetarium, demonstrated what will become a weekly noontime ritual of catching sunlight from the first-surface mirror as it hits the ground and marking the spot with a brick at precisely 12:12 Eastern Standard Time.

The sun of course keeps local solar time, not Eastern Standard Time and that extra 12 minutes past noon accounts for the correction to mean solar time as seen from Westminster Maryland.

The resulting difference between local solar time and mean solar time throughout the year is know as the Equation of Time and the path the sun will follow is the analemma. The sun’s excursion during the year travels not only north and south of the celestial equator by 23o ½  degrees, but performs a double east-west swing of  about +/- 15 minutes during the year … exceeding or lagging mean solar time, resulting in a figure 8.

The Westminster Astronomical Society intends to place a brick into the ground at the sunspot mark each week, resulting in a giant path of bricks that trace out the figure 8 of the analemma as cast as 12:12pm onto the grassy field.  Read more of Jon Kelvey's article at: carroll_county_times

While helping a friend with a camera obscura project, the idea for a mirror to trace the analemma came quickly to Bob who wants to popularize astronomy and get his town behind their Astronomical Society and Science, Technology, Engineering, and Mathematics (STEM).

As the Westminster Astronomical Society looks for a permanent site to house their telescopes, they’re looking for a way to make their presence known.  And perhaps what a better way than to create an analemmatic sundial?  Manchester, you too may have a sundial in your midst.