Photographic Magnitude
Related Category: Astronomy: General
see magnitude.
More on Photographic Magnitude
Magnitude - in astronomy, measure of the brightness of a star or other celestial object.
Photographic Magnitude
The magnitude of an object as measured on the traditional photographic emulsions, which are sensitive to a slightly bluer region of the spectrum than is the human eye. (mph)(antiquated term)
Photoionization ...
Photographic magnitude
Hertzsprung-Russell diagram - Relates absolute magnitude or luminosity versus spectral color or surface temperature.
Jansky radio astronomer's preferred unit - linear in power/unit area ...
photographic magnitude (NASA SP-7, 1965) (symbol mpg)
Stellar magnitudes measured from a photographic plate exposed without filters.
Photographic plates are more sensitive to short wavelengths than the human eye.
Also called a photographic magnitude as it approximates the blue spectral response of photographic film. B spectral class Very hot blue-white stars (10,000 - 28,000 K effective temperature). Characterised by neutral He lines.
north polar sequence (NASA SP-7, 1965) A list of stars near the north celestial pole arranged in order of photographic magnitude, used as reference stars in stellar photometry.
It was soon apparent, however, that the photographic magnitudes did not agree very well with those obtained visually. The reason for this is that early photographs responded mainly to blue light whereas the eye responds best to greenish-yellow.
Working at Harvard College Observatory, Leavitt calibrated the photographic magnitudes of 47 stars precisely to act as standard references or 'candles' for the magnitudes of all other stars.
Karl Schwarzschild discovered that the color of a star, and hence its temperature, could be determined by comparing the visual magnitude against the photographic magnitude.
The nebula has a visual magnitude of 8.8, and a photographic magnitude of 9.7. It is expanding at a rate of approximately 1 arcsecond per century (corresponding to 20-30 km/s). Its mass is approximately 1.2 solar mass.
Because ordinary photographic plates are more sensitive to blue light than is the eye, photographic magnitude is sometimes called blue magnitude.
The photograph became a valuable astronomical tool. Karl Schwarzschild discovered that the color of a star, and hence its temperature, could be determined by comparing the visual magnitude against the photographic magnitude.
A Dictionary of Earth Sciences entry for magnitude, earthquake
The Columbia Encyclopedia, Sixth Edition entry for visual magnitude
The Columbia Encyclopedia, Sixth Edition entry for photographic magnitude ...
 See also: Astronomy, Magnitude, Earth, Distance, Atmosphere
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