1. Unit 5, Topic 2
Telescopes

2. Basic Parts of a Telescope
Optical Lens (both)
Objective Lens (refracting)
Secondary Mirror (reflecting)
Brain Pop – Telescopes and Galileo

3. Refracting and Reflecting

4. Refracting

5. Reflecting

6. Resolving Power
To build a more powerful telescope, you need to increase its resolving power.
Resolving power is the fineness of detail the telescope can produce of the object in view. This depends on the diameter of the objective lens.

7. Refractors give better images than equal-size reflectors, but reflectors can be made much larger.
New designs have elements of both types of telescope.

8. Interferometry Combining telescopes for greater power
The resolution of the images seen with optical telescopes can be further improved when two or more of the telescopes are used together.
This technique of using telescopes in combination is known as interferometry.

9. Hubble Space Telescope
Although remote mountains make excellent sites for building and operating telescopes away from light pollution and air pollution, astronomers are still at the mercy of the weather. Clouds, humidity (moisture in the air), and even high winds can interfere with star-gazing.

10. Hubble Space Telescope
The development of the Hubble Space Telescope offers a solution to these problems. Orbiting about 600 km above Earth, the Hubble Space Telescope (a reflecting telescope) uses a series of mirrors to focus light from extremely distant objects.

11. Hubble Space Telescope

12. Hubble Facts
Just over 13 m in length and 4.3 m in diameter at its widest point.
It is modular in design.
Each orbit that the Hubble makes around Earth takes about 95 min.
While the telescope works 24 h a day, not all of that time is spent observing and sending data to Earth. Some time also goes to activities such as turning the telescope to focus on a new object of interest.

13. Remember from Topic 1 Earth Centred - Geocentric
Aristotle (helped by Pythagoras and Euclid’s math)
Ptolemy - Epicycles
Sun Centred – Heliocentric
Copernicus (still has epicycles)
TELESCOPES – Galileo (confirmed it was sun centred
Kepler - planets do not move in circles, but ellipses

15. Universal Gravitation
Eighty years later, Isaac Newton stated the law of universal gravitation. This law provided an explanation for the planets’ elliptical orbits.

16. Universal Gravitation - Newton
When no forces act on an object, it will move in a straight line at a constant speed.
The force of gravity pulls them in toward the Sun, which balances their tendency to move in a straight line.
The result is an orbit for each planet.