BoPlanets 1.3-Up2

Dialup	(56k)	-	24 s
ISDN	(128k)	-	11 s
DSL	(512k)	-	03 s
Cable	(1024k)	-	02 s
T1	(1484k)	-	01 s

BoPlanets is a virtual planetarium, which shows the positions of the planets in the sun system relative to an observing planet, which can be selected out of the planets and the sun. The planets can be shown in various views. In the ecliptic view the Cartesian coordinates, in the equatorial view right ascension and declination, in the horizontal view azimuth and altitude of the planets relative to an observing planet are displayed. In the horizontal view the position of the observer on the observing planet can be selected out of a list of locations or directly by its longitude and latitude.

You may have a look to the epicycles of the planets, when the earth was seen as the center of the planet system. Or you may observe the course of the sun as seen from the mercury, where the sun seems to go backwards and then forwards again. You can also change several orbital parameters in order to see the effect on the planet's orbital.