Types of Telescopes

[IMAGE] Newtonian Optical Path

$[IMAGE] Refractor Optical Path$

[IMAGE} Scmidt-Cassegrain Optical Path

What the heck are those numbers?

Calculations
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.

[JUMPback to top of this page]

Seattle Community Network Links: SCN FAQ | SCN Registration | SCN Policy | SCN Home Page