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2.16 Brightness


Frank L. Preuss


Vollmondfull moon
Venus (Max.) Venus (max.)
Mars (Max.) Mars (max.)
Jupiter (Max.) Jupiter (max.)
Sirius Sirius
Merkur (Max.) Mercury (max.)
Saturn (Max.) Saturn (max.)
Wega Vega
Polarstern polar star
Uranus Uranus
Beobachtungsgrenze für das bloße AugeObservation boundary for naked eye
Neptun (Max.) Neptune (max.)
Pluto (Max.) Pluto (max.)
schwächste noch photographierbare Sterneweakest stars still able to be photographed
"A Die astronomische Helligkeitsskale (Größenklassen m)"
"A The astronomical brightness scale (magnitudes m)"

The star Vega has a magnitude of 0.04. The name means "the rushing down eagle" and is in the constellation Lyra. Sirius is the brightest star in the sky with -1.42 magnitude. The sun’s is -26.86.


"In astronomy the also today still normal scale of the brightness of heavenly bodies goes already back to Hipparch in the essential features. He divided the stars into six orders of size, which we describe today with 1m, 2m, . . ., 6m. The meaning of m = magnitudo (Latin size). But it must be emphasized that this information has nothing to do with the actual size of the stars. According to Hipparch the stars of size 1 were the brightest; the stars of size 6 only just visible to the naked eye. Later the scale was expanded for the telescopic stars above 6m: 7m, 8m etc. Stars 23m can only just be photogaphed with the most light intensive instruments with long eposure time. On the other hand the scale was expanded to the other side for very bright stars, planets, as well as for sun and moon: 0m, -1m, -2m etc. The visual brightness of the sun is -26,86. The orders of size are subdivided decimally for more exact data. The human eye is only just able to register a difference of about 0.1."


Table of brightest stars


B Tabelle der hellsten Sterne

B Table of brightest stars




World map showing daylight around 13:00 UTC, April 2nd.


Length of daylight


Approximate length of daylight, in hours, as a function of latitude and time of year.


Light in water



This is the end of "2.16 Brightness"
To the German version of this chapter: 2.16 Helligkeit



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