| Definitions of the Terms | The Term |
| light is gathered and focused by a lense | |
| the spreading of light into a spectrum | |
| light is gathered and focused by mirrors | |
| a telescopes ability to discern detail | |
| disturbance of light as it passes through an opening | |
| measure of the ability to collect light | |
| device consisting of two or more telescopes | |
| adjusting a telescopes mirror to compensate for atmospheric distortions | |