| A | B |
|---|
| concave | shape of the primary mirror |
| convex | shape of the objective lens |
| refracting telescope | uses a lens to gather light |
| reflecting telescope | uses a mirror to gather light |
| focus | point where all the light rays converge |
| focal length | distance from the objective to the focus |
| objective | the main lens or mirror of a telescope |
| Cassegrain telescope | has a hole drilled in the primary mirror |
| Newtonian reflector | reflects the light out the side of the tube |
| eyepiece | magnifies the image |
| power | focal length of objective divided by focal length of eyepiece |
| area of a lens (or mirror) | pi r squared |
| counter clockwise | the way all the stars seem to rotate around Polaris |
| HST | Hubble Space Telescope |
| seeing | when the stars seem to "twinkle" |
| resolution | being able to see 2 objects that are close together |
| CCD | charge coupled device |
| clock drive | compensates for the Earth's rotation |
| finder scope | used to help locate objects in the large telescope |
| adaptive optics | used to correct for bad "seeing" |
