Calculations
As the amount of light received actually depends on the thickness of the Earth's atmosphere in the line of sight to the object, the apparent magnitudes are adjusted to the value they would have in the absence of the atmosphere. The dimmer an object appears, the higher its apparent magnitude. Note that brightness varies with distance; an extremely bright object may appear quite dim, if it is far away. Brightness varies inversely with the square of the distance. The absolute magnitude, M, of a celestial body (outside the Solar System) is the apparent magnitude it would have if it were 10 parsecs (~32.6 light years) away; that of a planet (or other Solar System body) is the apparent magnitude it would have if it were 1 astronomical unit away from both the Sun and Earth. The absolute magnitude of the Sun is 4.83 in the V band (yellow) and 5.48 in the B band (blue).
The apparent magnitude, m, in the band, x, can be defined as,
- ,
where is the observed flux in the band x, and and are a reference magnitude, and reference flux in the same band x, such as that of Vega. An increase of 1 in the magnitude scale corresponds to a decrease in brightness by a factor of . Based on the properties of logarithms, a difference in magnitudes, can be converted to a variation in brightness as .
Read more about this topic: Apparent Magnitude
Famous quotes containing the word calculations:
“Nowhere are our calculations more frequently upset than in war.”
—Titus Livius (Livy)
“The vulgar call good fortune that which really is produced by the calculations of genius.”
—Ralph Waldo Emerson (1803–1882)
“Now, since our condition accommodates things to itself, and transforms them according to itself, we no longer know things in their reality; for nothing comes to us that is not altered and falsified by our Senses. When the compass, the square, and the rule are untrue, all the calculations drawn from them, all the buildings erected by their measure, are of necessity also defective and out of plumb. The uncertainty of our senses renders uncertain everything that they produce.”
—Michel de Montaigne (1533–1592)