Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key


Play button


Play button




Click to flip

43 Cards in this Set

  • Front
  • Back
achromatic lens
A telescope lens composed of two lenses ground from different kinds of glass and designed to bring two selected colors to the same focus and correct for chromatic aberration. (p. 82)
active optics
Thin telescope mirrors that are controlled by computers to maintain proper shape as the telescope moves. (p. 89)
adaptive optics
A computer-controlled optical system used to partially correct for seeing in an astronomical telescope. (p. 89)
alt-azimuth mounting
A telescope mounting that allows the telescope to move in altitude (perpendicular to the horizon) and in azimuth (parallel to the horizon). See also equatorial mounting. (p. 89)
A unit of distance. 1 angstrom = 10-10 m. Commonly used to measure the wavelength of light. (p. 79)
atmospheric window
Wavelength region in which our atmosphere is transparent - at visual, infrared, and radio wavelengths. (p. 80)
binding energy
The energy needed to pull an electron away from its atom. (p. 95)
black body radiation
Radiation emitted by a hypothetical perfect radiator. The spectrum is continuous, and the wavelength of maximum emission depends on the body's temperature. (p. 97)
Cassegrain focus
The optical design in which the secondary mirror reflects light back down the tube through a hole in the center of the objective mirror. (p. 88)
See charge-coupled device.
charge-coupled device (CCD)
An electronic device consisting of a large array of light-sensitive elements used to record very faint images. (p. 90)
chromatic aberration
A distortion found in refracting telescopes because lenses focus different colors at slightly different distances. Images are consequently surrounded by color fringes. (p. 81)
comparison spectrum
A spectrum of known spectral lines used to identify unknown wavelengths in an object's spectrum. (p. 91)
diffraction fringe
Blurred fringe surrounding any image, caused by the wave properties of light. Because of this, no image detail smaller than the fringe can be seen. (p. 83)
electromagnetic radiation
Changing electric and magnetic fields that travel through space and transfer energy from one place to another; examples are light or radio waves. (p. 78)
equatorial mounting
A telescope mounting that allows motion parallel to and perpendicular to the celestial equator. (p. 89)
A short-focal-length lens used to enlarge the image in a telescope. The lens nearest the eye. (p. 80)
false-color image
A representation of graphical data with added or enhanced color to reveal detail. (p. 90)
focal length
The focal length of a lens is the distance from the lens to the point where it focuses parallel rays of light. (p. 80)
A piece of material in which numerous microscopic parallel lines are scribed. Light encountering a grating is dispersed to form a spectrum. (p. 91)
The observing technique in which separated telescopes combine to produce a virtual telescope with the resolution of a much-larger-diameter telescope. (p. 87)
light pollution
The illumination of the night sky by waste light from cities and outdoor lighting, which prevents the observation of faint objects. (p. 84)
light-gathering power
The ability of a telescope to collect light. Proportional to the area of the telescope's objective lens or mirror. (p. 82)
magnifying power
The ability of a telescope to make an image larger. (p. 84)
nanometer (nm)
A unit of distance equaling one-billionth of a meter (10-9 m). (p. 79)
Newtonian focus
The optical design in which a diagonal mirror reflects light out the side of the telescope tube for easier access. (p. 88)
objective lens
In a refracting telescope, the long-focal-length lens that forms an image of the object viewed. The lens closest to the object. (p. 80)
objective mirror
In a reflecting telescope, the principal mirror (reflecting surface) that forms an image of the object viewed. (p. 80)
A quantum of electromagnetic energy. Carries an amount of energy that depends inversely on its wavelength. (p. 78)
polar axis
In an equatorial telescope mounting, the axis that is parallel to Earth's axis. (p. 89)
primary lens
In a refracting telescope, the largest lens. (p. 80)
primary mirror
In a reflecting telescope, the largest mirror. (p. 80)
prime focus
The point at which the objective mirror forms an image in a reflecting telescope. (p. 88)
radio interferometer
Two or more radio telescopes that combine their signals to achieve the resolving power of a larger telescope. (p. 93)
reflecting telescope
A telescope that uses a concave mirror to focus light into an image. (p. 81)
refracting telescope
A telescope that forms images by bending (refracting) light with a lens. (p. 81)
resolving power
The ability of a telescope to reveal fine detail. Depends on the diameter of the telescope objective. (p. 83)
Schmidt-Cassegrain focus
The optical design that uses a thin corrector plate at the entrance to the telescope tube. A popular design for small telescopes. (p. 88)
secondary mirror
In a reflecting telescope, a mirror that directs the light from the primary mirror to a focal position. (p. 88)
Atmospheric conditions on a given night. When the atmosphere is unsteady, producing blurred images, the seeing is said to be poor. (p. 83)
sidereal drive
The motor and gears on a telescope that turn it westward to keep it pointed at a star. (p. 89)
A device that separates light by wavelengths to produce a spectrum. (p. 91)
The distance between successive peaks or troughs of a wave. Usually represented by the Greek letter lambda. (p. 78)