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 | Annapolis   | Sundial: 1036 | 
  | State/Province:  Maryland | Country:  USA | 
  | Dial Type:  Noon Mark or Meridian Dial | Condition:  Good | 
  |   | Latitude and Longitude: | 38° 58.927' N  76° 29.547' W | 
  | Location: | 
  | On the campus of St. John's College, southeast of  McKeldin Planetarium, in front of Mellon Hall on a small, circular brick plaza.
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	| Description: | 
	| This brass mariner's compass about 12 inches in diameter is mounted on the east side of a concrete pillar. It is known on campus as "The Ptolemy Stone".  It functions as a meridian transit with altitude marks every half degree engraved on the upper south quadrant.  The alidade has a notch on the upper end and a plate at the lower end, designed for measuring the altitude of the sun using the notch shadow (preventing eye damage of sighting the sun directly).  The pillar is just over 3 feet tall with a sloped top.  The main slope is that of the site latitude.  A steeper "north face" is cut plane to the celestial equator.  To make the equator "visible", a ring is mounted to the face.  The ring casts no shadow on the equinox and from September to March is in shadow.  A similar Ptolemy Stone is at St. John's campus in Santa Fe, NM.
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General Information: | Owner: St. John's College
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| Construction Date:  circa 1987 or earlier
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| References: | Web Links: | 
| St. John's is one of the oldest academic institutions in the US, a successor to King William's School founded in 1696.  SJC received a collegiate charter in 1784, providing  a liberal arts education based on Great Books curriculum.
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Last Revised: 2021-12-09 15:20