Comets

Erratic members of the Solar system, usually of small mass. Luminous bodies, wandering through space, or circulating around the Sun, and visible only when they approach the Sun. They usually consist of three elements: nucleus, envelope, and tail. The superstitious once considered them to be evil omens. Those pursuing an elongated orbit are periodic and … Read more

Circles of Position

Circles intersecting the horizon and meridian, and passing through a star: in terms of which to express the position of the star. Their use is not obsolete. However, Circles of Position were not so used by Ptolemy or Placidus, who measured the distance of every star by its semi-arc. DeVore, Nicholas. Encyclopedia of Astrology. New … Read more

Celestial Sphere

If one pictures the sphere we call the Earth, enlarged to embrace the visible heavens, the resulting concept can be called the celestial sphere. If it is a true sphere, any circle drawn around it can be termed a circumference. To locate any particular circle as a circumference, implies the selection of some point of … Read more