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chapter 3
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38
Astronomy
12th Grade
12/04/2013

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Term
active optics
Definition
a technology used with reflecting telescopes developed in the 1980s, which actively shapes a telescope's mirrors to prevent deformation due to external influences such as wind, temperature,
Term
adaptive optics
Definition
a technology used to improve the performance of optical systems by reducing the effect of wavefront distortions. ...
Term
angular resolution
Definition
the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object, thereby making it a major determinant of image resolution.
Term
cassegrain focus
Definition
a combination of a primary concave mirror and a secondary convex mirror,
Term
charge-coupled device (CCD)
Definition
charge-coupled device, a high-speed semiconductor used chiefly in image detection.
Term
coude focus
Definition
telescope in which light from the primary mirror is reflected along the polar axis to additional mirrors, and in which the focus (coudé focus)  is independent of the telescope's motion.
Term
electromagnetic spectrum
Definition
the range of wavelengths or frequencies over which electromagnetic radiation extends
Term
eyepiece lens
Definition
a type of lens that is attached to a variety of optical devices such as telescopes and microscopes.
Term
focal length
Definition
the distance between the center of a lens or curved mirror and its focus.
Term
focal plane
Definition
the plane through the focus perpendicular to the axis of a mirror or lens
Term
focal point
Definition
the point at which rays or waves meet after reflection or refraction, or the point from which diverging rays or waves appear to proceed.
Term
frequency
Definition
the rate at which a vibration occurs that constitutes a wave, either in a material  or in an electromagnetic field
Term
gamma ray
Definition
penetrating electromagnetic radiation of shorter wavelength than X-rays.
Term
infrared radiation
Definition
electromagnetic radiation with wavelengths longer than visible light but shorter than radio waves
Term
light-gathering power
Definition
A measure of the light-gathering ability of a telescope
Term
magnification
Definition
the action or process of magnifying something or being magnified, esp. visually.
Term
newtonian reflector
Definition
reflecting telescope in which the image is viewed through an eyepiece perpendicular to main axis
Term
objective lens
Definition
the lens in a telescope or microscope nearest to the object observed
Term
photon
Definition
a particle representing a quantum of light or other electromagnetic radiation. A photon carries energy proportional to the radiation frequency but has zero rest mass.
Term
pixel
Definition
a minute area of illumination on a display screen, one of many from which an image is composed
Term
primary mirror
Definition
the principal light-gathering surface of a reflecting telescope
Term
prime focus
Definition
the focal point of the objective lens or primary mirror of a telescope
Term
radio telescope
Definition
an instrument used to detect radio emissions from the sky, whether from natural celestial objects or from artificial satellites.
Term
radio wave
Definition
an electromagnetic wave of a frequency between about 104 and 1011 or 1012 Hz, as used for long-distance communication.
Term
reflecting telescope (reflector)
Definition
A telescope in which light from the object is gathered and focused by a concave mirror, with the resulting image magnified by the eyepiece
Term
reflection
Definition
the throwing back by a body or surface of light, heat, or sound without absorbing it
Term
refracting telescope
Definition
a telescope that uses a converging lens to collect light
Term
schmidt corrector plate
Definition
spheric lens which is designed to correct the spherical aberration in the spherical primary mirror it is combined with.
Term
secondary mirror
Definition
the second deflecting or focusing mirror element in a reflecting telescope. Light gathered by the primary mirror is directed towards a focal point typically past the location of the secondary.
Term
seeing disk
Definition
Astronomical seeing refers to the blurring and twinkling of astronomical objects such as stars caused by turbulent mixing in the Earth's atmosphere varying the optical refractive index.
Term
spectrum
Definition
a band of colors, as seen in a rainbow, produced by separation of the components of light by their different degrees of refraction according to wavelength.
Term
spherical aberration
Definition
a loss of definition in the image arising from the surface geometry of a spherical mirror or lens.
Term
twinkling
Definition
shine with a gleam that varies repeatedly between bright and faint.
Term
ultraviolet radiation (uv)
Definition
radiation lying in the ultraviolet range; wave lengths shorter than light but longer than X rays
Term
very - long - baseline - interferometry (VLBI)
Definition
a type of astronomical interferometry used in radio astronomy. In VLBI a signal from an astronomical radio source, such as a quasar, is collected at multiple radio telescopes on Earth. ...
Term
wavelength
Definition
the distance between successive crests of a wave, esp. points in a sound wave or electromagnetic wave
Term
focus ( of an ellipse)
Definition
two fixed points on the interior of an ellipse used in the formal definition of a curve.
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