AS101 Lecture Notes - Generic Point, Celestial Pole, Declination
Document Summary
When we talk about mapping the sky, e are thinking about objects (stars, planets, etc. ) as if they were on the surface of an imaginary sphere, the celestial sphere that surrounds the earth. You can make maps of the celestial sphere much as you can make maps of the earth"s surface. Astronomers have divided the celestial sphere into 88 constellations with well-defined boundaries. There are several ways to describe the location of something in the sky. We can also describe in which constellation something is located. Every star is in one and only one of the 88 constellations. Astronomers distinguish constellations (regions of the celestial sphere) from asterisms, which are patterns or groups of stars, more like landmarks. A given star may be part of more than one asterism. Rigel is part of the foot of orion and is also part of the winter. One of the things a map should tell us about is the distances between places.
