| A | B |
|---|
| right ascension | measured in hours and minutes |
| declination | could have been called "celestial latitude" |
| Celestial Equator | 0 degree declination |
| Prime Meridian | 0 degrees longitude on Earth |
| Vernal Equinox/Celestial Prime Meridian | 0/24 hours RA on the Celestial Sphere |
| celestial sphere | spherical "map" where night sky objects are found |
| precession | Earth's wobble |
| Time necessary for one precession | roughly 26 000 years |
| how often locations on the celestial sphere are updated | every 50 years |
| Zenith | located right above you no matter where you are |
| Nadir | located right below you |
| Azimuth | "direction" of an object from Earth's north pole relative to an observer |
| Altitude | Angle of a celestial object above the horizon relative to the observer |
