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Glossary
Narrow-Band Filter A filter that covers one spectral line.
Neutral Density Filter A very broad filter that removes light equally over a very
large range of wavelengths. These are normally used to cut down the light from
a bright source such as the Sun or Moon.
Neutrino A subatomic particle with zero charge and an extremely low mass. The
neutrino interacts weakly with matter and is produced in vast numbers during
nuclear synthesis.
Newtonian A reflecting telescope in which a flat mirror is set at 45
◦ to the primary
mirror and just inside the focal point so that the point of focus is outside the tube,
often close to the top.
Nodding Going off target; for example, when you cannot get a representative
background in the current image.
Parsec The distance at which an object would show a parallax displacement of
one second of arc. It equates to 3.08567758 × 10
16 m.
Pedestal The charge added to a pixel to prevent wraparound during mathematical
processes.
Perigee For an object in an orbit, this is the point at which it is closest to the object
it is orbiting.
Photoelectric Effect An effect by which certain materials produce a current only
when exposed to light of a certain wavelength.
Photometry The science of measuring the brightness of an object.
Pipeline A series of programmes used to process an image automatically.
Pixel Size The size of an individual pixel.
Planck’s Law A law of physics that describes the relationship between emission
and the temperature of a black body.
Planetary Nebula A nebula formed by the ejection of the outer layers of a red
giant.
Plate Solving A process by which the WCS transform for an image is found.
Point Spread Function In astronomy, how the light from a source spreads out
over the CCD. For a star, this should be a Gaussian distribution.
Polar Aligned In terms of telescope mounts, a mount one axis of which is aligned
with the celestial poles.
Polarisation Filter A filter that only lets pass photons whose electric field is orientated in a specific direction.
Population I Young stars like the Sun.
Population II Older stars such as found in globular clusters.
Population III The very first stars. Yet to be detected.
Propagation of Uncertainties The methods by which mathematical operations
affect errors.
Proper Motion The motion of an object against the background stars.
Proton–Proton Chain The nuclear process chain that converts hydrogen to helium,
resulting in the production of energy. There are four such chains, with a varying
degree of importance within a star, dependent on its mass.
Quantum Efficiency In relation to CCDs, the efficiency of the pixels at converting
photons to electrons.
Glossary
Narrow-Band Filter A filter that covers one spectral line.
Neutral Density Filter A very broad filter that removes light equally over a very
large range of wavelengths. These are normally used to cut down the light from
a bright source such as the Sun or Moon.
Neutrino A subatomic particle with zero charge and an extremely low mass. The
neutrino interacts weakly with matter and is produced in vast numbers during
nuclear synthesis.
Newtonian A reflecting telescope in which a flat mirror is set at 45
◦ to the primary
mirror and just inside the focal point so that the point of focus is outside the tube,
often close to the top.
Nodding Going off target; for example, when you cannot get a representative
background in the current image.
Parsec The distance at which an object would show a parallax displacement of
one second of arc. It equates to 3.08567758 × 10
16 m.
Pedestal The charge added to a pixel to prevent wraparound during mathematical
processes.
Perigee For an object in an orbit, this is the point at which it is closest to the object
it is orbiting.
Photoelectric Effect An effect by which certain materials produce a current only
when exposed to light of a certain wavelength.
Photometry The science of measuring the brightness of an object.
Pipeline A series of programmes used to process an image automatically.
Pixel Size The size of an individual pixel.
Planck’s Law A law of physics that describes the relationship between emission
and the temperature of a black body.
Planetary Nebula A nebula formed by the ejection of the outer layers of a red
giant.
Plate Solving A process by which the WCS transform for an image is found.
Point Spread Function In astronomy, how the light from a source spreads out
over the CCD. For a star, this should be a Gaussian distribution.
Polar Aligned In terms of telescope mounts, a mount one axis of which is aligned
with the celestial poles.
Polarisation Filter A filter that only lets pass photons whose electric field is orientated in a specific direction.
Population I Young stars like the Sun.
Population II Older stars such as found in globular clusters.
Population III The very first stars. Yet to be detected.
Propagation of Uncertainties The methods by which mathematical operations
affect errors.
Proper Motion The motion of an object against the background stars.
Proton–Proton Chain The nuclear process chain that converts hydrogen to helium,
resulting in the production of energy. There are four such chains, with a varying
degree of importance within a star, dependent on its mass.
Quantum Efficiency In relation to CCDs, the efficiency of the pixels at converting
photons to electrons.