| Telescope Types |
| What are those numbers? |
The f-ratio is the focal length divided by the diameter of the telescope. Magnification is the focal length of the telescope divided by the focal length of the eyepiece.Example:
To find the f-ratio of a telescope 10 " in diameter with a 45" focal length:
- Divide 45 " F.L. by10" D. to get an f-ratio of 4.5.
To compute magnification:
First, convert focal length to mm: 45" = 1146 mm, then:
- 1146 mm focal length divided by 35 mm eyepiece equals 33 magnification.