Chapter 1 Notes:

Chapter 20 Notes:

Unit I: Optical Telescopes

Most common type of telescope is the OPTICAL telescope

Use lenses and mirrors to gather light
Usually kept in domed buildings, under constant temperature & humidity
Designed to be able to rotate and tilt so that it will be able to stay pointed at an object all night (or day)

The Refracting Telescope

a. Since light passes through the glass lens, the lens must be perfect (completely flawless)

b. Lens must be ground to be perfect on both sides, not just one side like a mirror

c. Lens can only be supported by the edges, mirrors can be supported by entire back side

The Reflecting Telescope

The Multiple-Mirror Reflectors (Telescopes)

Referred to as the MMT
Uses several small mirrors rather than one large mirror
Several small mirrors are much cheaper to produce than making one large mirror
Each small mirror is focused on the eyepiece
The Keck MMT has 36 small mirrors
The Very Large Telescope (VLT) has 4 – 8.2m reflectors equal to a telescope with one 16 meter reflector

Other Optical Telescopes

The Schmidt telescope uses both refracting and reflecting properties - Produces very large, wide-angle views of space
The Hubble Space Telescope is designed to magnify images in space, from space! …the Hubble also detects ultraviolet light, not just visible light

Improving Images

Photographic plates help to create a time-lapse imprint of an image far away
The Charged-Coupled Device (CCD) uses photocells to gather light and is downloaded to a computer

Unit II: Studying Energy Beyond Visible Light

The Electromagnetic Spectrum consists of:

Electromagnetic energy is sent out in both frequency and wavelength

High Freq. = Short Wavelength

Low Freq. = Long Wavelength

Radio Astronomy – the study of radio waves (invisible light) whizzing through space.

ALL objects in space are said to emit some form of electromagnetic energy (nothing is invisible!)

Radio waves are unique because they can be detected 24 hours/day and in all types of conditions.

The Radio Telescope

A dish-shaped telescope capable of receiving radio waves from space
Usually built into the hollow of mountains (as seen on TV and James Bond movie)
Interferometry – using multiple smaller radio telescopes to collect data similar to one huge, costly telescope
Two 10ft telescopes 100ft. apart have the same power is one 100ft. telescope
Telescopes are also designed specially for all forms of data collection from the electromagnetic spectrum

Unit III: Visible Light

The Spectroscope

Each color of light has a different wavelength – therefore you see colors as "different"
The band of colors that forms is called the visible spectrum
A Spectroscope can be used to separate all the colors of the "rainbow" – It usually contains a small eyepiece lens and a PRISM (triangular shaped glass lens)
A Spectrograph is just like a spectroscope but also contains a camera to photograph the visible spectrum
Astronomers can conclude the following about a given stars visible spectrum

Various Kinds of Spectra

Continuous spectra = a band of unbroken colors (true rainbow effect)
Bright-line spectra = unevenly spaced series of lines of different colors and brightness
Dark-line spectra = a continuous spectra with dark lines where light is absorbed (usually caused from light passing through a gas)