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Topic: Visual magnitude

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	Absolute Visual Magnitude - Hutchinson encyclopedia article about Absolute Visual Magnitude (Site not responding. Last check: 2007-11-07)
		In astronomy, measure of the intrinsic brightness of a celestial body in contrast to its apparent brightness or magnitude as seen from Earth.
		For a non-self-luminous body, such as an asteroid, the absolute magnitude is the magnitude it would appear to have if it were one astronomical unit (149.6 million km/92.6 million mi) from both the Sun and the Earth with the phase angle zero.
		For a self-luminous body, such as a star or galaxy, the absolute magnitude is the magnitude it would appear to have if it were at a distance of 10 parsecs or 32.616 light years.
	encyclopedia.farlex.com /Absolute+Visual+Magnitude (162 words)

	Apparent magnitude - Wikipedia, the free encyclopedia
		The brightest stars were said to be of first magnitude (m = 1), while the faintest were of sixth magnitude (m = 6), the limit of human visual perception (without the aid of a telescope).
		For this purpose the UBV system is widely used, in which the magnitude is measured in three different wavelength bands: U (centred at about 350 nm, in the near ultraviolet), B (about 435 nm, in the blue region) and V (about 555 nm, in the middle of the human visual range in daylight).
		The V band was chosen for spectral purposes and gives magnitudes closely corresponding to those seen by the light-adapted human eye, and when an apparent magnitude is given without any further qualification, it is usually the V magnitude that is meant, more or less the same as visual magnitude.
	en.wikipedia.org /wiki/Apparent_magnitude (1115 words)

	Absolute magnitude - Wikipedia, the free encyclopedia
		In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standardized distance away.
		For comparison, Sirius has an absolute magnitude of 1.4 and the Sun has an absolute visual magnitude of 4.83 (it actually serves as a reference point).
		In this case, the absolute magnitude is defined as the apparent magnitude that the object would have if it were one astronomical unit (au) from both the Sun and the Earth and at a phase angle of zero degrees.
	en.wikipedia.org /wiki/Absolute_magnitude (709 words)

	Magnitude
		Apparent magnitude is the brightness of an object as it appears to an observer on Earth.
		Visual magnitude is the magnitude measured when using the light to which the human eye responds.
		Photographic magnitude is the magnitude measured by a standard photographic emulsion, which responds chiefly to the blue and violet part of the spectrum (although different photographic materials have very different colour responses).
	www.historyoftheuniverse.com /magnitude.html (618 words)

	Stellar Magnitudes
		The former is a convolution of the true brightness and the effect of distance on the observed brightness, because the intensity of light from a source decreases as the square of the distance (the inverse square law).
		However, the apparent magnitude is not so useful because it mixes up the intrinsic brightness of the star (which is related to its internal energy production) and the effect of distance (which has nothing to do with the intrinsic structure of the star).
		The apparent magnitude of various objects determined using light from the visible part of the spectrum is given in the adjacent table.
	csep10.phys.utk.edu /astr162/lect/stars/magnitudes.html (802 words)

	What Is Visual Magnitude? (Site not responding. Last check: 2007-11-07)
		"Visual magnitude" is a scale used by astronomers to measure the brightness of a star.
		The term "visual" means the brightness is being measured in the visible part of the spectrum, the part you can see with your eye (usually around 5500 angstroms).
		This means a difference in magnitudes of 5 units (from magnitude 1 to magnitude 6, for example) corresponds to a change in brightness of 100 times.
	liftoff.msfc.nasa.gov /academy/universe/MAG.HTML (385 words)

	Apparent magnitude -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-11-07)
		The absolute magnitude of the Sun is +4.83 in the V band (yellow) and +5.48 in the B band (blue).
		This original system did not measure the magnitude of the (A typical star that is the source of light and heat for the planets in the solar system) Sun.
		For an object with a given ((astronomy) the magnitude that a star would have if it were viewed from a distance of 10 parsecs (32.62 light years) from the earth) absolute magnitude, 5 is added to the apparent magnitude for every tenfold increase in the distance to the object.
	www.absoluteastronomy.com /encyclopedia/a/ap/apparent_magnitude.htm (1239 words)

	The Apparent Brightness of Deep Sky Objects (Site not responding. Last check: 2007-11-07)
		At a visual magnitude of 6.5, for example, one might be led to believe that NGC 7293 (the Helix Nebula) would be readily visible in an 8 inch telescope since such an instrument has a limiting magnitude of about 13.5.
		Although its published magnitude indicates that this object is bright, it is in fact one of the more difficult deep sky objects, comparable to the Owl Nebula, requiring the best of observing conditions and perhaps a nebula filter to render it visible.
		Using the total visual magnitude of M57 (9.0) as a standard, M97 would appear as a 9 + 3.9 = 12.9 magnitude object as indicated in the last column, me, which is the effective visual magnitude relative to M57.
	www.monmouth.com /~ksears/loso4.htm (1497 words)

	WHO \| Magnitude and causes of visual impairment
		Globally, in 2002 more than 161 million people were visually impaired, of whom 124 million people had low vision and 37 million were blind.* However, refractive error as a cause of visual impairment was not included, which implies that the actual global magnitude of visual impairment is greater.
		This estimate was later extrapolated to the 1996 world population (45 million blind), and to the projected 2020 world population (76 million), indicating a twofold increase in the magnitude of visual impairment in the world by 2020.
		The extent of the global burden of visual impairment in 2002 is not strictly comparable to the previous estimates of 1990, which indicated there were 148 million visually impaired, of which 38 million were blind.
	www.who.int /mediacentre/factsheets/fs282/en (1105 words)

	Sea and Sky: Messier Objects M1 - M10
		In the center of this nebula is a 16th magnitude star which is the collapsed core of the supernova.
		With a visual magnitude of 6, this nebula can be easily seen in the constellation of Sagittarius with the naked eye on a dark, clear night.
		With a visual magnitude of 6.6 and an apparent diameter of 15 arc minutes, this is one of the best clusters to be viewed with both binoculars and small telescopes.
	www.seasky.org /astronomy/astronomy_messier_1to10.html (827 words)

	visual magnitude
		The apparent magnitude of a celestial body in a wavelength range approximating that of the human eye.
		This is usually different from photographic magnitude because photographic emulsions do not exactly match the way the human eye's sensitivity varies with wavelength.
		Visual magnitude is now essentially synonymous with V magnitude, which is determined photometrically.
	daviddarling.info /encyclopedia/V/visual_magnitude.html (129 words)

	Stellar Magnitudes
		The brightest stars were of 1st magnitude, while the faintest that could be seen in a dark, clear sky were 6th magnitude.
		Magnitudes are analogous to the decibel unit used for specifying power ratios.
		This is the absolute magnitude of the sun, or its visual magnitude when seen from a distance of 10 parsecs.
	www.du.edu /~jcalvert/astro/magnitud.htm (4825 words)

	Sea and Sky: Messier Objects M31 - M40
		Its close proximity gives it a visual magnitude of 8.1, which is quite bright for a galaxy.
		M36 has a visual magnitude of 6.3 with the individual member stars ranging in magnitude from 9 to 14.
		With a visual magnitude of 5.2, it is a bright cluster although very loosely populated.
	www.seasky.org /astronomy/astronomy_messier_31to40.html (857 words)

	ipedia.com: Apparent magnitude Article (Site not responding. Last check: 2007-11-07)
		The apparent magnitude of a star, planet or other heavenly body is a measure of its apparent brightness ; that is, the amount of light received from the object.
		The rate at which apparent brightness changes, as the distance from an object increases, is calculated by the inverse-square law.
		The absolute magnitude, M, of an object, is the apparent magnitude it would have if it were 10 parsecs away.
	www.ipedia.com /apparent_magnitude.html (871 words)

	Limiting Visual Magnitude Determination
		The limiting visual magnitude is technically defined as the faintest magnitude that can be seen by the unaided eye at the zenith.
		The limiting visual magnitude is often used as an indicator of atmospheric transparancy and the general quality of the observing conditions at an observing site.
		Also, since the limiting magnitude is defined as the faintest star that can be seen at the zenith, the actual limiting magnitude could be somewhat fainter than that observed unless the sky region used was actually at the zenith for the observer.
	phys-astro.sonoma.edu /observatory/observers/limiting_magnitude.html (1165 words)

	The Herschel 400 List -- Brighter Than You Think
		The faintest Herschel 400 object, according to the Astronomical League's data, is NGC 6540, with visual magnitude given as 14.5.
		The second-faintest Herschel 400 object, according to the Astronomical League's data, is NGC 6369, with a visual magnitude of 14.0 given.
		The third- and fourth-faintest objects, according to the Astronomical League's data, are the planetary nebulae NGC 1501 and NGC 7008, both with magnitudes given as 13.5, but with recent visual magnitudes of 11.5 and 10.7 respectively.
	astro.isi.edu /reference/herschel.html (1036 words)

	Sacramento Peak: Magnitude (Site not responding. Last check: 2007-11-07)
		A difference of five magnitudes corresponds to a brightness ratio of exactly 100: a star of magnitude 0 is 100 times as bright as a star of magnitude 5, and 10,000 (= 100 times 100) times as bright as a star of magnitude 10.
		The limiting magnitudes are as seen from the Earth: the Hubble Space Telescope in space might gain another 1.5 magnitudes because it does not have to look through an atmosphere that blurs and scatters light.
		How long one has to expose a picture to record a very faint object depends on the magnitude of the object, on the optical quality of the instrument, on the length of the exposure, on the efficiency of the recording device, and on whether the object is point-like or extended.
	www.sunspot.noao.edu /sunspot/pr/answerbook/magnitude.html (1988 words)

	Arkansas Sky Observatory - 2001 Limiting Magnitude (Site not responding. Last check: 2007-11-07)
		Visual limiting magnitude MUST be differentiated from PHOTOGRAPHIC magnitude, in that the camera's film (and CCD imaging) has the ability to accumulate light, like a "sponge" slowly soaking up water.
		4) the visual acuity of the observer; and,
		A third and best alternative would be to use a "visual back" that accepts eyepiece onto the rear cell of the telescope and view directly through the instrument, making your view exactly that of the charts.
	www.arksky.org /limmag.htm (1264 words)

	Light Curve Templete/Observing Form For Visual SNe Observers.
		Observing forms for logging magnitude estimates (form, sncurv.gif) and the templete forms (avcurv.gif, snetem.gif) which are uncluttered versions of the templete are presented, and are intended for use in comparing individual or aquired observations verses the mean SN Type Ia, V magnitude light curve (BL).
		An analysis of amateur magnitude estimates involving the bright supernova SN 1989B in NGC 3627 (M66) is displayed.
		It may be prudent to use the templete's snetemp.gif and/or avcurv.gif to register any corrections (to magnitude) AFTER the data points have been obtained and noted on form and sncurv.gif, thus eliminating a tendency for bias towards the mean light curves which might influence the intended outcome....
	www.sai.msu.su /mirrors/isn/snecurv.htm (693 words)

	Herschel-400 list -- brighter than you think
		The magnitudes given by the Astronomical League are asserted to be visual ones, though rather old.
		I investigated objects for which a magnitude 12.5 or fainter was given, as well as those for which no magnitude was provided.
		Some of the objects for which I found no visual magnitude are galaxies with blue magnitudes faint enough to suggest that their visual magnitudes might also exceed 12.0.
	observers.org /reports/99.04.04.html (782 words)

	The Visual Photometry of Comets :
		The visual photometry of comets requires that certain standard methods be followed, so that the data will be meaningful and comparable with results from other observers.
		The magnitude estimates may be analysed to determine the object's intrinsic brightness, and the pattern of variation of magnitude with changing distance to the sun.
		The determination of the integrated magnitude of an object whose brightness is superficially distributed over an extended area, is a much more complex procedure than, for instance, estimating the magnitude of a variable star, where both the object being measured and the comparison stars, all look point-like.
	cometforum.planetaclix.pt /meth.html (3142 words)

	Sky Publishing - The Stellar Magnitude System (Site not responding. Last check: 2007-11-07)
		Since then the history of the magnitude scale is, like so much else in astronomy, the history of increasing scientific precision being built on an ungainly historical foundation that was too deeply rooted for anyone to bulldoze it and start fresh.
		The resulting magnitude scale is logarithmic, in neat agreement with the 1850s belief that all human senses are logarithmic in their response to stimuli.
		U encompasses the near-ultraviolet, B is blue, and V corresponds fairly closely to the old visual magnitude; its wide peak is in the yellow-green band, where the eye is most sensitive.
	www.wwnorton.com /astro21/sandt/starmags.html (1451 words)

	A Note on the Apparent Brightness of Deep Sky Objects (Site not responding. Last check: 2007-11-07)
		In this article Frank pointed out the important difference between the so-called visual magnitude (mv) and the "extended" magnitude (me) of deep sky objects, that is, galaxies, globular clusters and planetary nebulae.
		In practice, it would be preferable to have a formula which relates the extended magnitude to the visual magnitude and the dimensions of the object.
		The conclusion which can be reached is that not only the visual magnitude is of importance but equally important is its dimension.
	www.monmouth.com /~ksears/collett.htm (996 words)

	Curious About Astronomy: What is apparent magnitude?
		Thus, you might have expected that if the magnitude scale were set up "correctly", the difference in brightness between a magnitude 1 and magnitude 2 star would be the same as the difference in brightness between a magnitude 2 and magnitude 3 star -- this would be a so-called linear brightness scale.
		That is, a magnitude 2 star is around 2.5 times fainter than a magnitude 1 star, while a magnitude 3 star is around 2.5 times fainter than a magnitude 2 star and therefore 2.5 x 2.5 = 6.3 times fainter than a magnitude 1 star.
		So the way we find that the Sun has a visual magnitude of -26.74 is that we measure how bright it appears from Earth and observe that we receive around 51 billion times as much light from the Sun as we do from Vega.
	curious.astro.cornell.edu /question.php?number=569 (929 words)

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