| A | B |
|---|
| Astronomy | the study of all physical objects beyond Earth. |
| Calendar | Asystem for organizing time within a single unit called a year.. |
| Year | The time required for the Earth to orbit the sun once. |
| Month | Roughly the amount of time for the moon to orbit the Earth once. |
| Day | the time required for the Earth to rotate once. |
| Leap Year | The year an entire day is added to the calendar. |
| Constellation | A section of the sky that contains a recognizable star pattern. |
| Altitude | the angle between an object in the sky and the horizon. |
| Right Ascension | A measure of howfar East an object isfrom the point at wicih the sun appears on the firts day of Spring. |
| Declination | A measure of how far north or south of the clelstial equator an object is. |
| Celestial Equator | An imaginary circle created by extending the Earth's equator into space. |
| Ecliptic | the apparent path the sun takes across the celestial sphere each year. |
| Light Year | An unit of lenght equal to the distance light travel through sace in a year. |
| Telescope | An instrument that collects electromagnetic radiation from the sky and concentrates it for better observation. |
| Refracting Telescope | A telescope that uses a set of lenses to gather and focus light.. |
| Reflecting Telescope | A telescope that uses a set of mirrors to gather and focus light/ |
| Electromagnetic Spectrum | All the wave lenghts of electromagnetic radation. |
