Telescopes….

Telescopes are helpful to astronomers because they….

• Collect more light• Separate distant objects….• Magnify the image• Detect other wavelengths…

Telescopes and Domes

Optical Telescopes; * use lenses and mirrors to gather and focus

starlight.* the light gathering power depends on the area of the lens or mirror.

There are 2 types of optical telescopes………..

Refracting…• Has two lenses..

• Uses large objective lens to gather and focus light.

• Most in use today are almost 100 years old.

Reflecting telescope…

• Uses one large curved mirror to gather and focus starlight.

MMT multiple-mirror telescope

• This telescope has several mirrors that take the place of one mirror..

• Spectroscope: separates starlight into colors.

3 kinds of visible spectrum…

• Continuous – unbroken band of colors. Source is sending out energy of all wavelengths.

• Bright line – Source is sending out only certain wavelengths of energy. (also called emission spectra)

• Dark-line – continuous spectrum with dark lines. Helps identify composition.

Radio Telescope• Collects radio waves and feeds them to

a receiver, where they are changed into electrical signals.

• What are some advantages that a radio telescope has over an optical???????

Lenses……

• It is a transparent material that bends or refracts light.2 main types of lenses;

• Convex: thick in the middle. Bending light inward. Amount of refraction depends on how curved the lens is.

• Concaved: thin in the middle. Bends light away from the lens. (spreads apart)

Top: a convex lens converges light raysBottom: a concave lens diverges light rays

Images• Real image: one that can be projected

onto a screen. The image is upside down..

• Virtual image: when an object is placed between a convex lens and its focal point producing a larger and upright.

i.e… (magnifying glass)

Space Telescopes

• The Hubble Telescope was designed to take pictures of the whole universe.

• What major advantage does the Hubble have over ground based telescopes?????

Pictures from the Hubble Space Telescope

Doppler Shift (effect)• Sometimes the black lines in a star’s

spectrum are shifted to the Red or Blue end of the spectrum.

• These shifts occur because of a change in the distance between the star and Earth.

• When the distance increases (moving away) = shifted toward the longer wavelength (RED).

• When the distance decreases (moving closer) = shifted toward the shorter wavelength (BLUE).