Glossary
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Quantum Mechanics The fundamental branch of physics that describes the universe at the atomic and subatomic length scales.
Rayleigh Criterion The non-Airy resolution of a telescope.
Read Noise Noise created by the process of reading the CCD.
Readout Noise Noise associated with the ADU.
Residual Bulk Image Ghost images caused by saturation in a previous image
SALSA J A freeware multiplatform application designed to perform time series
photometry.
SAO DS9 A FITS manipulation package built by the Smithsonian Astronomical
Observatory.
Saturation The point at which a pixel is full and can detect no further photons
during an exposure.
Schmidt–Cassegrain A class of reflecting telescope based on the Ritchey and
Chrétien design but with a correcting plate.
Science Frame A light frame that has had dark, bias, and flat frames applied.
Seeing The angular dispersion of stars caused by atmospheric turbulence.
Sexagesimal Notation The description of angles as hours, minutes, and seconds
(or degrees, minutes, and seconds) as opposed to decimal degrees.
Shot Noise Noise that originates from the discrete nature of the source, for example
from a photon or electron.
Sidereal Time Time as based on the Earth’s rotation measured relative to the fixed
stars rather than the Sun.
Signal-to-Noise Ratio The radio between the source signal and the noise. High
signal-to-noise data has less uncertainty.
Sky Brightness The intensity of the light being emitted and reflection of the sky.
The sky brightness is the main limiting factor in deep-sky observations.
Sky Flats Flat frames that use the twilight sky as the illumination source.
Small Circle A circle on the surface of a sphere whose diameter does not intersect
the centre of the sphere, that is, a circle that is not a great circle.
Spectrum The rainbow-like distribution of light made by a spectrograph.
Spectrograph A device that splits light regions of similar wavelengths.
Spherical Aberration An optical problem associated with spherical mirrors.
Light rays incident at different points on the mirror come to focus at different
points. The Hubble Space Telescope famously suffered from spherical aberration.
Stopping Down Reducing the aperture of a telescope.
Summing Co-adding images.
Surface Brightness The magnitude per unit area.
Transit Telescope A telescope designed just to observe objects as they cross the
meridian.
Transmission Window A region in the electromagnetic spectrum to which a body
is transparent. This term typically refers to the Earth’s atmosphere.
229
Quantum Mechanics The fundamental branch of physics that describes the universe at the atomic and subatomic length scales.
Rayleigh Criterion The non-Airy resolution of a telescope.
Read Noise Noise created by the process of reading the CCD.
Readout Noise Noise associated with the ADU.
Residual Bulk Image Ghost images caused by saturation in a previous image
SALSA J A freeware multiplatform application designed to perform time series
photometry.
SAO DS9 A FITS manipulation package built by the Smithsonian Astronomical
Observatory.
Saturation The point at which a pixel is full and can detect no further photons
during an exposure.
Schmidt–Cassegrain A class of reflecting telescope based on the Ritchey and
Chrétien design but with a correcting plate.
Science Frame A light frame that has had dark, bias, and flat frames applied.
Seeing The angular dispersion of stars caused by atmospheric turbulence.
Sexagesimal Notation The description of angles as hours, minutes, and seconds
(or degrees, minutes, and seconds) as opposed to decimal degrees.
Shot Noise Noise that originates from the discrete nature of the source, for example
from a photon or electron.
Sidereal Time Time as based on the Earth’s rotation measured relative to the fixed
stars rather than the Sun.
Signal-to-Noise Ratio The radio between the source signal and the noise. High
signal-to-noise data has less uncertainty.
Sky Brightness The intensity of the light being emitted and reflection of the sky.
The sky brightness is the main limiting factor in deep-sky observations.
Sky Flats Flat frames that use the twilight sky as the illumination source.
Small Circle A circle on the surface of a sphere whose diameter does not intersect
the centre of the sphere, that is, a circle that is not a great circle.
Spectrum The rainbow-like distribution of light made by a spectrograph.
Spectrograph A device that splits light regions of similar wavelengths.
Spherical Aberration An optical problem associated with spherical mirrors.
Light rays incident at different points on the mirror come to focus at different
points. The Hubble Space Telescope famously suffered from spherical aberration.
Stopping Down Reducing the aperture of a telescope.
Summing Co-adding images.
Surface Brightness The magnitude per unit area.
Transit Telescope A telescope designed just to observe objects as they cross the
meridian.
Transmission Window A region in the electromagnetic spectrum to which a body
is transparent. This term typically refers to the Earth’s atmosphere.