Glossary
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International Astronomical Union (IAU) The governing body for astronomy
made up of professional astronomers from around the world.
Interstellar Reddening The reddening of light from an object, caused by the
preferential scattering of short wavelengths over long ones.
IRAF A professional Linux data reduction package for astronomy.
Isotropically In every direction. Most stars radiate isotropically.
Jansky A unit of flux used in radio astronomy.
Julian Date A standard dating system using the day as the base unit with the origin
at noon on 1 January 4713 BCE.
Lab Book A journal containing a complete description of all observations and
experiments including calculations and observations. A good lab book should
enable other investigators to reproduce the lab book’s author’s experiments.
Light Frame The unprocessed digital image of an astronomical object.
Light Pollution Any source of manmade stray light.
LIDAR An optical version of radar used in atmospheric physics and the detection
of small objects and changes in distance.
Limb Darkening The effect whereby the edges of gaseous bodies such as stars
appear to darken at the edge.
Linearly Polarised Polarised to the linear orientation of the photon’s electric field
rather than its rotational orientation.
Local Sidereal Time The sidereal time local to an observer.
Lucky Imaging A imaging technique using a high-speed video camera in order
to produce high-resolution images.
Luminance Frame An image normal in clear, used to enhance detail in a colour
image.
Luminosity The total amount of energy radiated by a body over a specific bandwidth. If calculated over the entire spectrum, it is known as the bolometric luminosity.
Lyman Series A series of hydrogen lines caused by the transition of an electron
to a lower energy level.
Magnification The ratio of the angular size of an object seen through a telescope
and seen with the naked eye.
Main Sequence The area of the HR diagram that represents stars that are core
hydrogen burning.
Maksutov–Cassegrain A catadioptric that uses the correcting plates as the reverse
of the secondary.
Master Frames A calibration frame made by combining multiple frames.
Mean Solar Time The mean time as measured by the Sun, whose principal unit
is the day.
Meridian The great circle on a sphere perpendicular to the planes of the celestial
equator and horizon.
Meridian Flip A problem with equatorially mounted telescopes that requires them
to “flip” over when a source crosses the meridian.
Metallicity The ratio of hydrogen to another heavy element, normally iron, in a
star.
227
International Astronomical Union (IAU) The governing body for astronomy
made up of professional astronomers from around the world.
Interstellar Reddening The reddening of light from an object, caused by the
preferential scattering of short wavelengths over long ones.
IRAF A professional Linux data reduction package for astronomy.
Isotropically In every direction. Most stars radiate isotropically.
Jansky A unit of flux used in radio astronomy.
Julian Date A standard dating system using the day as the base unit with the origin
at noon on 1 January 4713 BCE.
Lab Book A journal containing a complete description of all observations and
experiments including calculations and observations. A good lab book should
enable other investigators to reproduce the lab book’s author’s experiments.
Light Frame The unprocessed digital image of an astronomical object.
Light Pollution Any source of manmade stray light.
LIDAR An optical version of radar used in atmospheric physics and the detection
of small objects and changes in distance.
Limb Darkening The effect whereby the edges of gaseous bodies such as stars
appear to darken at the edge.
Linearly Polarised Polarised to the linear orientation of the photon’s electric field
rather than its rotational orientation.
Local Sidereal Time The sidereal time local to an observer.
Lucky Imaging A imaging technique using a high-speed video camera in order
to produce high-resolution images.
Luminance Frame An image normal in clear, used to enhance detail in a colour
image.
Luminosity The total amount of energy radiated by a body over a specific bandwidth. If calculated over the entire spectrum, it is known as the bolometric luminosity.
Lyman Series A series of hydrogen lines caused by the transition of an electron
to a lower energy level.
Magnification The ratio of the angular size of an object seen through a telescope
and seen with the naked eye.
Main Sequence The area of the HR diagram that represents stars that are core
hydrogen burning.
Maksutov–Cassegrain A catadioptric that uses the correcting plates as the reverse
of the secondary.
Master Frames A calibration frame made by combining multiple frames.
Mean Solar Time The mean time as measured by the Sun, whose principal unit
is the day.
Meridian The great circle on a sphere perpendicular to the planes of the celestial
equator and horizon.
Meridian Flip A problem with equatorially mounted telescopes that requires them
to “flip” over when a source crosses the meridian.
Metallicity The ratio of hydrogen to another heavy element, normally iron, in a
star.