nass_news_2012_aug_al-shatir_dialAt 3pm on August 15th Roger Bailey of the North American Sundial Society will hold a public lecture on the historic Ibn al-Shatir sundial at the Great Falls Library in VA.  The Analemma Society proposes to recreate the dial’s design, adapted for the latitude of Observatory Park, The Turner Farm, in Great Falls, VA.

Hopefully this will be the second major dial at Observatory Park maintained by the Analemma Society in conjunction with the Fairfax County Park Authority. The first dial was a commemorative dial designed and built by Tony Moss for the 400th anniversary of Jamestown, VA.

“High on the minaret of the Great Mosque in Damascus is a remarkable sundial created by Ibn al-Shatir in 1371. Through the 10th to 14th centuries the science of astronomy, timekeeping and sundials had advanced in major Moslem centres like Cairo and Damascus. Based on the developing science of timekeeping, Ibn al-Shatir designed a unique instrument that was a breakthrough…The sundial features equal hours rather than the previous system of dividing the day into 12 hours regardless of the seasonal changes.”

Three different time systems are drawn on the dial, reading time from sunrise, sunset and noon. “The dial has reference lines for all five Moslem prayer times, even those at daybreak and nightfall when the sun was well below the horizon. This sundial was the first to use a polar gnomon, parallel to the earth’s axis and pointed north… The dial represents technological changes anticipating the design of sundials created later in the Islamic Middle East and Christian Europe….”

UPDATE: "We are very much looking forward to Roger's talk next Wednesday and hope that many in the Great Falls community and nearby can attend. Faculty and students from the George Mason Ali Vural Ak Center for Global Islamic Studies and the Georgetown University Islamic Studies Department have stated interest in attending."

"Presentations about the Ibn al-Shatir Sundial are not new to the Great Falls area. In August 2006 an exhibit about the sundial that was prepared by Charles Olin and a friend of the Analemma Society, Barbara Smith, was displayed at the Great Falls Library. In September 2006, the exhibit was moved to the McLean Community Center.  It is splendid that Roger is able to stop here on his way to the North American Sundial Society meeting in Ashville. We look forward to greeting him."

Charles and Jacque Olin of the Analemma Society

[Material cited is, in part, from a bulletin published by Jeff Kretsch of the Analemma Society and email from The Analemma Society.  To become a member, go to]