AY 101 Lecture Notes - Lecture 2: 33Rd Parallel North, Tuscaloosa, Alabama, Celestial Equator
Document Summary
An imaginary sphere against which all celestial objects project. Horizon allows us to see only half. Sphere rotates, with stars continuously rising and setting relative to horizon. The exte(cid:374)sio(cid:374) of the ea(cid:396)th"s e(cid:395)uato(cid:396) o(cid:374)to the (cid:272)elestial sphe(cid:396)e. Extensions of the sphere poles onto the celestial sphere. The (cid:862)(cid:374)o(cid:396)th sta(cid:396)(cid:863), polaris is a bright star that happens to lie in the direction of the north celestial pole. The angle of polaris above the northern horizon point equals your latitude. Rising and setting motions are caused by earth rotation. Earth rotates west to east, making stars appear to rise in the east half of the sky and set in the west. Every star follows a path on the celestial sphere called a diurnal (daily) circle: the size of the circle depends on the location of a star relative to the celestial equator. Adding the horizon limits what parts of the diurnal paths we can actually see.
