Other
Constellations Web Page: The Constellations
Information about 88 constellations, including the myths associated with them and details of the major astronomical objects that are part of them.
Wolfram Research
Wolfram Math World: Apothem
MathWorld offers a definition of the apothem of a circle as well as an illustration is provided on this page. An equation is also provided to calculate the apothem of a circle given the radius and the sagitta.
Curated OER
Sagittarius the Archer
The Learning Network surveys several constellations and the twelve constellations that comprise the Zodiac. Features include star tables and symbols.