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DIMENSIONS: MAGNIFICATIONS USING FOCAL LENGTH

ratio
INDEX
Focal Length
When a reflecting mirror is made, the depth of the parabolic curve on it's face determines it's focal length. The light is concentrated to a point and magnified by the eyepiece. The distance between the center of the mirror and the point of it being focused by the eyepiece is the focal length.

A refracting telescope's lens is similar except the light travels through the lens where it is bent by its curvature to the focal length and then magnified by the eyepiece.

Eyepieces also have focal lengths and these are written in millimeters on the side. When you know your telescope's focal length and also your
magnifications
dimensions
TELESCOPE LINKS:
Basics
Mounts
Light Gathering Power
Closer Look At Refractors
Closer Look At Reflectors
Balancing
Eyepieces
Cleaning Optics
eyepieces, the magnifications
of each eyepiece can be worked out.
Tips
Divide the length of the eyepiece into the length of the telescope.
Astrophotography
Build your own telescope
Example telescope Tasco 302012 Newtonian Reflector
Build your own telescope
for schools
Binoculars eg. Telescope Focal Length 900mm Eyepiece Focal Length 20mm & 4mm

900/20 = 45 The magnification is 45x for the 20mm eyepiece.
900/4=225 The magnification is 225x for the 4mm eyepiece.
Aperture Size
The diameter of the main mirror or lens of a telescope is the aperture (size). This is usually expressed in millimeters, but because of the American influence on telescopes a lot of the sizes are produced in inches. The typical apertures of reflectors are:
Imperial
3"
4.5"
6"
8"
10"
12.5"
16"
18"
Metric
76mm
114mm
150mm
200mm
254mm
317.5mm
406mm
457mm
telescopes
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magnifications
INDEX
focal ratio

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