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TELESCOPES
Where do we put telescopes to
have the best viewing
conditions?
1. On Earth:
CLEAR
HIGH
DRY
COLD
DARK
Problem with Telescopes on
Earth?
Problem:
Particles of all sorts in the
atmosphere block and cloud the view
2. In Space
Solves atmosphere problem –
CLEAR VIEW!
Examples: Hubble, Cobe , Iras
Problem with telescopes in space?
They’re in space!
Hard to get to
Hard to repair
EXPENSIVE!!!
Functions of a Telescope
1.
2.
3.
4.
Collect Light
Magnify Images
Separate Distant Objects
Use as a Camera
OPTICAL TELESCOPES
(USE VISIBLE LIGHT)
Two types:
1. Refractor –
BENDS LIGHT
Invented by Hans Lippershey in 1608
Refined by Galileo in 1609
Galileo demonstrating his telescope
2. Reflector –
USES MIRRORS
Tololo Observatory - Chile
TYPE 1 – REFRACTING TELESCOPE
How does it work?
a.
b.
It bends light to create an image
It uses two lenses
1. eyepiece (ocular) lens - small
2. objective lens
- large
Draw it!
Type 2 – Reflecting Telescope
a.
b.
c.
Invented by Isaac Newton in 1668
Uses two mirrors
Objective Mirror – Large
Secondary (flat) mirror – Small
Can be VERY LARGE 40 ft - 50 ft
diameter objective mirror!
Draw It!
Advantages of a reflector
1.
2.
You only need to prepare one
side of the mirror. (on a
refractor the lens has two
sides) – cheaper and
distortion is less of a
problem.
The whole back of the mirror
can be supported, therefore
can be made very LARGE
Non-optical Telescopes
1.
Radio Telescopes
a. Location – Earth
(atmosphere does not affect radio waves)
b. Structure –
Large metal dish
c. Size –
very large because radio waves
have a very long wavelength
d. Arrays –
sets of multiple radio
telescopes that allow for more data to be
gathered.
Ex –
VLA (very large array) in Socorro, New Mexico
27 dishes.
SETI– Search for Extra-Terrestrial Intelligence
looking for intelligent radio signals
Other Non-Optical Telescopes
(all are satellites)
a.
Infrared – IRAS launched 1983
b. Microwaves –
COBE Cosmic Background
explorer. Discovered evidence of the Big
Bang. Launched 1981
COBE Image of CBR
c. X-Rays –
Chandra Launched 1999
Cassiopeia Super Nova
Black Hole
Crab Nebula
Saturn
d. Gamma Rays –
GRO Gamma Ray Observatory
Milky Way