1. Telescopes

2. Why Telescopes are Important
We spend a lot of time talking about light and images
But none of that does us any good if we don’t have a way of collecting that light in the first place
This is where telescopes come in

3. What is a Telescope? So just what is a telescope?
An object that uses lenses or reflecting surfaces to collect light from a distant object

4. The History of the Telescope
It is a common misconception that Galileo invented the first telescopes
In fact, Hans Lippershey, a Dutch spectacle make, is credited with designing the first telescope
Galileo is the first person known to have turned a telescope to the sky(he gets the credit)

5. Galileo’s Telescope He was astonished by what he saw
The rings of Saturn
Stars in the Milky Way
The moons of Jupiter
Spots on the sun
He also went blind-----

6. Can You Imagine?
Just imagine what he must have felt, being the first person to see these things
It was all completely unexpected-----
Galileo’s observations, and those of others, would literally change the course of human history

7. Telescopes Today Telescopes have come a long way since then
The biggest single telescopes have main mirrors that are over 12 meters in diameter!
Some telescopes are actually arrays that are made of dozens of smaller telescopes linked together

8. Largest GranTeCan or GTC 10.4m

9. Keck 1 & 2 USA , Hi
10M

10. Tied for 3rd at 9. 2m The Hobby-Eberly Telescope or HET Ft
Tied for 3rd at 9.2m The Hobby-Eberly Telescope or HET Ft. Davis, Texas

11. The Giant Magellan Telescope or GMT in 2020 will have 7-8
The Giant Magellan Telescope or GMT in 2020 will have 7-8.4m mirrors(24.5m)

13. Today, there are telescopes that are designed to see radio, microwave, infrared, visible, ultraviolet, x-ray and gamma-ray light?
True
False

14. How Telescopes Work There are two main types of telescopes
Refracting telescopes use lenses to focus light to a point
Reflecting telescopes use mirrors to focus the light
Catadioptric telescopes are a combination of the two

15. Refracting and Reflecting Telescopes

16. Anatomy of a Telescope
Although there are many types of telescopes, all have some basic key parts

17. Anatomy of a Telescope Aperture Primary Secondary Eyepiece
Optical Tube
Finder
Detector

18. Anatomy of a Telescope
The aperture is simply the part of the telescope that lets light in
The primary bends the light, bringing the rays to a point
The secondary aids in this process

19. Focusing Light The idea of focusing light is important
Telescopes collect light from a large area
By focusing the light, we concentrate its power
The focal plane is the plane where the light rays meet
The focal length is the distance from the primary lens (or mirror) to the focal plane

20. Focusing Light

21. Focusing Light

22. The Focal Plane
If we put our eye at the focal plane, we would only see a bright point
The eye piece straightens out the rays of light so our eye can see the image
If we move the eyepiece out of the focal plane, the image will be distorted

23. Anatomy of a Telescope
The optical tube protects the rest of the telescope and blocks stray rays of light
The finder is a small telescope used for honing in on objects
The detector is the thing that actually records the light
Could be your eye

24. Common Reflectors

25. Some Other Telescope Properties
There are some other properties of telescopes that astronomers are interested in
Some of these things are
Collecting Area
Resolution
Magnification
Cost

26. What is the most important property of a telescope for astronomers?
Magnification
Collecting Area
Focal Length

27. Collecting Area
Collecting area is the area of the surface that the telescope uses to collect light
This is usually the primary lens or mirror
Many people think that magnification is the most important property of a telescope, but it is actually collecting area

28. Collecting Area Why is collecting area important?
Suppose you are trying to see a very faint source
If it is faint, then it is not sending many photons to Earth
We need to collect as many photons as we can
Having a large collecting area does this – like casting a big net to catch more fish

29. Collecting Area
Most astronomical objects are pretty faint, so we need to collect as much light as we can

30. Resolution
The resolution of a telescope defines how much detail we can see
All optical systems have some resolution limit
Eventually, the separation between objects becomes too small for us to see

31. Angular Size We measure the separation of objects in terms of angles
Remember that there are 360° in a full circle
There are 60 arc minutes in a degree, and 60 arc seconds in an arc minute
So there are 3600 arc seconds for every degree of sky.

33. Back To Resolution Consider looking at a distant mountain
Although the mountain is covered in trees, we cannot make out the trees themselves
Our eyes have too low of a resolution