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 rays Bottom: 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).