// readme.txt

//  

// NightSky Applet

// Joseph Snow

// ASPIRE PRO

// Aug 31, 2000





*** good seasons lesson with drawings

http://www.synapses.co.uk/astro/less17.html



*** night sky example from Julie

http://www.astro.wisc.edu/~dolan/constellations/java/Cepheus.html



*** another cool night Sky example

http://www.skycalendar.com/skycal/index.html



*** info about kepler and eleptical orbits

http://www.xylem.demon.co.uk/kepler/index.html#top



*** solar system info

http://seds.lpl.arizona.edu/nineplanets/nineplanets/data.html



*** Earth's Seasons, aphelion and perihelion dates

http://aa.usno.navy.mil/AA/data/docs/EarthSeasons.html



eccentricity 

the eccentricity of an ellipse (planetary orbit) is the ratio of the distance between the foci and the major axis. Equivalently the eccentricity is (ra-rp)/(ra+rp) where ra is the apoapsis distance and rp is the periapsis distance. 



aphelion 

the point in its orbit where a planet is farthest from the Sun; when refering to objects orbiting the Earth the term apogee is used; the term apoapsis is used for orbits around other bodies. (opposite of perihelion) 



perihelion 

the point in its orbit where a planet is closest to the Sun. when referring to objects orbiting the Earth the term perigee is used; the term periapsis is used for orbits around other bodies. (opposite of aphelion)