1.
2.
They can collect far more light than the unaided eye
They can magnify very small images
Different Types of Optical Telescopes
( uses lenses and mirrors to gather and focus starlight)
1. refracting telescope – bends or refracts starlight through the first lens to focus the image through the second lens (the eye piece)
2. reflecting telescope – uses one large curved mirror to focus starlight
3. multiple-mirror telescopes – many reflecting mirrors working in unison to produce larger, higher resolution images

Refracting Telescope

Reflecting Telescope

Mt Palomar 200" Reflecting Telescope

Multiple-Mirror Telescope Observatory in Mt. Hopkins, Arizona

Schmidt Telescope – uses both reflecting mirrors and refracting lenses

Hubble Telescope – reflecting telescope orbiting Earth, has unparalleled resolution and usable for ultraviolet detection that is not possible from Earth’s surface

Spectroscope – uses a prism to separate visible light and determine the chemical composition of a star
E.W. Maunder (at the eyepiece) and W.
Bowyer observing with the half-prism spectroscope, c. 1894

Radio Telescope – very large telescope that picks-up radio waves emitted by quasars and pulsars
Arecibo in Puerto Rico (1000’ dia.)
The Very Large Array (VLA) in
San Agustin, NM →→→→→

Electromagnetic Spectrum
 The elecromagnetic spectrum includes all forms of radiation,
7% of which is visible light -- the radiation to which our eyes
 are sensitive.
The spectrum up according to the wavelength of the radiation.

Electromagnetic Spectrum

Doppler Effect
The apparent change in the wavelength due to an object's motion
Sound: like the whistle on a train or a car horn as it goes past.

Doppler Effect
Red shift – as an object moves away – the wavelength the star radiates gets longer … toward the RED end of the spectrum
 The faster the distance increases the greater the
‘Red Shift’
The object is moving away from us

Doppler Effect
Blue shift – as an object moves toward – the wavelength the star radiates gets shorter … toward the BLUE end of the spectrum
 The faster the distance decreases the greater the
‘Blue Shift’
The object is moving toward US

Parallax the apparent displacement of an observed object due to a change in the position of the observer http://sci2.esa.int/interactive/media/flashes/2_1_1.htm

Parallax http://sci2.esa.int/interactive/media/flashes/2_1_1.htm