Telescopes

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Telescopes

Chapter 3

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Objectives

To know the general types of telescopes and the advantages and disadvantages of each one.

To know the primary parts and functions of each part of a telescope.

To know the importance of the diameter of the objective and to know how the magnification of a telescope is related to the focal lengths of the objective and eyepiece.

To know the advantages and disadvantages of earth and space-based telescopes.

Slide 5

Galileo Galilei (1564-1642)

Slide 6

History

invented by Dutch lens maker in 1608

Galileo: small 30X scope

Observed the moon and “began” the modern age of Astronomy where measurement was more important than philosophy

Slide 7

Galileo noticed

moons orbiting Jupiter

phases of Venus

craters on the moon

sunspots

This was strong evidence that Copernicus was right although Galileo wasn’t willing to die for it.

Slide 8

How a telescope works

gathers light through the objective (mirror or lens)

bigger is better because it gathers more light

ability to see faint objects increases proportionally with the square of the radius of the objective

focuses light

viewed through an eyepiece (changing the eyepiece changes the magnification)

magnification is the ratio of the focal length of the objective to the focal length of the eyepiece

Slide 9

General types of telescopes

Refracting (objective is a lens)

Reflecting (objective is a mirror)

Newtonian

Cassegrain

Catadioptrics

uses mirrors and lenses

Schmidt-Cassegrain

Maksutov-Cassegrain

Slide 10

Refractors (glass lens)

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Advantages and Disadvantages

Easy to use and reliable

Excellent for lunar, planetary and binary star observing especially in larger apertures.

High contrast images with no secondary mirror or diagonal obstruction.

Sealed optical tube reduces image degrading air currents and protects optics.