Magnitude (astronomy)
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In astronomy, magnitude is measure of the brightness of an object, usually in a defined passband. An imprecise but systematic determination of the magnitude of objects was introduced in ancient times by Hipparchus.
Light sources of different magnitudes. A very bright satellite flare can be seen in the night sky.
Apparent magnitude
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Apparent magnitude is a measure of the brightness of a star or other astronomical object to an observer on Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance, and any extinction of the object's light caused by interstellar dust along the line of sight to the observer.
Asteroid 65 Cybele and two stars, with their magnitudes labeled
Image of 30 Doradus taken by ESO's VISTA. This nebula has a visual magnitude of 8.