Photographic magnitude
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Photographic magnitude (mph or mp ) is a measure of the relative brightness of a star or other astronomical object as imaged on a photographic film emulsion with a camera attached to a telescope. An object's apparent photographic magnitude depends on its intrinsic luminosity, its distance and any extinction of light by interstellar matter existing along the line of sight to the observer.
Photographic observations have now been superseded by electronic photometry such as CCD
Method
Prior to photographic methods to determine magnitude, the brightness of celestial objects was determined by visual
By the late 19th Century, an improved measure of the
Early black and white photographic plates used silver halide emulsions that were more sensitive to the blue end of the
Photographic photometric methods define magnitudes and colours of astronomical objects using astronomical photographic images as viewed through selected or standard coloured
Magnitudes and colour indices
Apparent photographic magnitude is usually given as mpg or mp, or photovisual magnitudes mp or mpv.[3][1] Absolute photographic magnitude is Mpg.[3] These are different from the commonplace photometric systems (UBV, UBVRI or JHK) that are expressed with a capital letter. e.g. 'V" (mV), "B" (mB), etc. Other visual magnitudes estimated by the human eye are expressed using lower case letters. e.g. "v" or "b", etc.[4] e.g. Visual magnitudes as mv.[3] Hence, a 6th magnitude star might be stated as 6.0V, 6.0B, 6.0v or 6.0p. Because starlight is measured over a different range of wavelengths across the electromagnetic spectrum and are affected by different instrumental photometric sensitivities to light, they are not necessarily equivalent in numerical value.[4]
See also
- Apparent magnitude
- Absolute magnitude
- Araucaria Project
- Magnitude (astronomy)
- Photometry (astronomy)
- Surface brightness
References
- ^ Bibcode:2007JBAA..117..172M.
- ISBN 978-1-107-63612-5.
- ^ ISBN 0-582-03163-X.
- ^ a b MacRobert, A. (1 August 2006). "The Stellar Magnitude System". Sky and Telescope. Retrieved 21 May 2019.