TELESCOPES. WHAT IS A TELESCOPE A telescope is an instrument that gathers electromagnetic radiation from objection in space and concentrates it for better.

TELESCOPES

WHAT IS A TELESCOPE

• A telescope is an instrument that gathers electromagnetic radiation from objection in space and concentrates it for better observation.

• What is electromagnetic radiation?

ELECTROMAGNETIC SPECTRUM• For thousands of years,

human have used their eyes to observe stars and planets. But scientists eventually discovered that visible light, the light we see is not the only for of radiation.

• The electromagnetic spectrum is made up of all of the wavelengths of the electromagnetic radiation.

• X-rays and gamma rays cannot pass through the earths atmosphere

OPTICAL TELESCOPES• Optical telescopes are the most common

type of telescope.

• They are used to study visible light from objects in the universe.

• Without using a telescope how many stars do you think you can see?

• Roughly 8000

• How many do you this you can see with a optical telescope?

• Millions!

OPTICAL TELESCOPES CONT.

• Optical telescopes collect visible light into a focal point.

• A focal point is the point where the rays of light that pass through a lens or reflect from a mirror.

• The simplest optical telescope has two lens• Objective lens – collects light (Bigger = more light)• Eye piece – magnifies the image produced by the objective lens.

TYPES OF OPTICAL TELESCOPES

• Refracting telescopes

• Reflecting telescopes

• Very large reflection telescopes

• Optical space telescopes

• Nonoptical telescopes

REFRACTING TELESCOPES

• Use lenses to gather and focus light

• Two disadvantages

• Lens focus different colors of light at slightly different distances, so it’s hard to focus

• The size of a refracting telescope is also limited by the size of the objective lens.• If the lens is too big the glass sags

under its own weight.

REFLECTING TELESCOPES

• A telescope that uses a curved mirror to gather and focus light

• Light enters the telescope and is reflected from a large curved mirror to a flat mirror

• Advantages• Allows are a very large mirror = more light!!• Light is not curved/distorted = allows for better focus

VERY LARGE REFLECTING TELESCOPES

• Very large reflecting telescopes several mirrors work together to gather light!

• More light = better image!

PROBLEMS WITH THE ATMOSPHERE

• The light gathered by telescopes on the Earth is affected by the atmosphere. The Earth’s atmosphere causes starlight to shimmer and blur due to motion of the air above.

• Also light pollution from large cities can make the sky look bright.

• How do you fix this problem?

PLACING OF TELESCOPES

• Most telescopes are placed in dry areas to avoid moisture.

• Mountain top a good place because the air is thinner.

• Mountain tops generally have less air and light pollution.

WHAT’S ANOTHER FIX FOR LIGHT POLLUTION?

• …

• Stick the telescope in space!

• One of our best microscopes, the Hubble Space Telescope, has a small mirror but can collect a lot of light due to its location.

NONOPTICAL TELESCOPES• Nonoptical telescopes detect

radiation that cannot be seen by the human eye• Astronomers study the entire

electromagnetic spectrum because each type of radiation reveals different clues about an object

• On the ground we can have radio telescopes because radio waves can penetrate the atmosphere

• For higher frequency radiation, which as x-rays and gamma rays, the telescope needs to be placed in space.