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Star Magnitude Brightness: stars are assigned a number starting with the brightest star starting at about -1 magnitude. Dimmer stars are zero or positive numbers. The larger the number means the dimmer the star is. For example, a star -1 magnitude is brighter than a star 0 magnitude. A star 0 magnitude is brighter than a star 1 magnitude. A star 1 magnitude is brighter than a star 2 magnitude. A star 4 magnitude is brighter than a star 5 magnitude. Magnitude sequence for stars starting with the brightest is -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 magnitude, ... etc. The First Magnitude Stars Table lists the brightest stars in the sky that are -1, 0 and 1 magnitude. Sirius is the brightest at -1.44 magnitude. These stars are referred to as First Magnitude stars since they are all 1 magnitude or brighter. Brightness of stars is assigned a number starting with the brightest star Sirius starting at 1.44 magnitude. Dimmer stars are positive numbers. The larger the number means the dimmer the star is. For example, a star -1 magnitude is brighter than a star 0 magnitude. A star 0 magnitude is brighter than a star 1 magnitude. A star 1 magnitude is brighter than a star 2 magnitude. Magnitude sequence for stars starting with the brightest is -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 magnitude, ... etc. Star names come from Greek, Latin and Arabic origins. For example, Sirius and Capella are of Greek and Latin origins and Vega, Rigel, Aldebaran are Arabic derivations. In some cases two names are given to a star because some stars are referred to with multiple names. The designation column gives the star's designation by Johann Bayer's letter and John Flamsteed's number. Johann Bayer's Uranometer star maps (1603) introduced the designating the brighter stars of each constellation by small letters of the Greek alphabet. In general, the stars are lettered in order of brightness. In a constellation the brightest star is Alpha, the second brightest Beta and so on. That is why most of the First Magnitude Stars are designated Alpha and a few are designated Beta. The full name of the star in the Johann Bayer system is the letter followed by the genitive (possessive) of the Latin name of the constellation. For example, Sirius is Alpha Canis Majoris. The below table uses the constellation abbreviations. Therefore, Sirius designation is Alpha CMa. A different plan used in John Flamsteed's Historia Coelestis (1729). The stars are numbered consecutively from west to east across the constellation. Therefore, in the John Flamsteed system Sirius is designated 9 Canis Majoris. In the Magnitude column the letter "c" refers to the combined magnitude of a double star and "v" refers to the median magnitude of a variable star. Star magnitude data is from the Hipparcos Catalog: First Magnitude Stars Table Name Designation Magnitude Sirius 9 Alpha CMa -1.44 Canopus Alpha Car -0.62 Rigil Kent or Alpha Centauri Alpha Cen -0.28c Acturus 16 Alpha Boo -0.05v Vega 3 Alpha Lyr 0.03v Capella 13 Alpha Aur 0.08v Rigel 19 Beta Ori 0.18v Procyon 10 Alpha CMi 0.40 Achernar Alpha Eri 0.45v Betelgeuse or Betelgeux 58 Alpha Ori 0.45v Agena or Hadar Beta Cen 0.61v Altair 53 Alpha Aql 0.76v Acrux Alpha Cru 0.77c Aldebaran 87 Alpha Tau 0.87 Spica 67 Alpha Vir 0.98v Antares 21 Alpha Sco 1.06v Pollux 78 Beta Gem 1.16 Fomalhaut 24 Alpha PsA 1.17 Beta Crucis Beta Cru 1.25v Deneb 50 Alpha Cyg 1.25v Regulus 32 Alpha Leo 1.36 The decimal point is not used when star magnitudes are used on a star map. The decimal point could be confused for a star on the map. At the top of this page is the constellation Ursa Minor with star magnitudes for some of its stars. For example, magnitude 31 on the star map mean 3.1 and magnitude 55 on the star map mean 5.5. Historically the magnitude system started with Hipparcos and Ptolemy when they divided the stars into six magnitudes. About 20 of the brightest stars that they could observe from their location were assigned to the first magnitude. The next set of bright stars were assigned to second magnitude and so forth. Sixth magnitude stars were assigned to stars that were barely visible to the unaided eye under favorable conditions. It was empirically determined that the ratio of first magnitude to sixth magnitude was 100 to 1. A logarithmic scale of 2.512 between magnitude levels is implemented. For example, a first magnitude star is 100 brighter than a sixth magnitude star or the sixth magnitude star is 1/100 or .01 dimmer that a first magnitude star. Second example, a fifth magnitude star is 2.512 times brighter than a sixth magnitude star or the sixth magnitude star is 1/2.512 or .40 dimmer that a fifth magnitude star. General rule, a star is 2.512 times brighter than a star one magnitude less. Six Star Magnitude Table Logarithmic scale of How Much Brighter Star Magnitude 2.512 X between magnitude levels than a Sixth Magnitude Star Starting at Sixth Magnitude 1 100 Times 2.51 x 2.51 x 2.51 x 2.51 x 2.51 2 39.8 Times 2.51 x 2.51 x 2.51 x 2.51 3 15.8 Times 2.51 x 2.51 x 2.51 4 6.3 Times 2.51 x 2.51 5 2.51 Times 2.51 x 6 With the invention of the telescope and modern equipment to measure star magnitudes the scale has been extended in both directions. Dimmer stars are assigned magnitudes larger than 6 ( 6, 7, 8, 9, ... 30th ... etc.) The Hubble Space Telescope Deep Field image contains some galaxies as faint as 30th magnitude. First magnitude stars are corrected across the scale of 1, 0, -1 with the brightest star Sirius at -1.44. The scale increases in brightness with negative numbers. For example, the brightest planet Venus varies in brightness and is about -4.4 magnitude at maximum brightness. The Moon is -12.7 magnitude at maximum brightness and the Sun is -26.75 magnitude. The below Star Magnitude Table Based on -1 Magnitude Star shows how much dimmer than a -1 magnitude star are stars to 19th magnitude. For example, most 10 x 50 or 7 x 50 binoculars can detect a 9 magnitude star. A 9 magnitude star is one tenth thousand (1/10,000 or .0001) dimmer than -1 magnitude star. Star Magnitude Table Showing How Much Dimmer other Magnitudes are as Compared to a -1 Magnitude Star Star Magnitude How Much Dimmer How Much Dimmer than a -1 Magnitude Star than a -1 Magnitude Star -1 0 1/2.51 0.398 1 1/6.31 0.158 2 1/15 0.063 3 1/39 0.0251 4 1/100 0.0100 5 1/251 0.00398 6 1/630 0.00158 7 1/1,584 0.000630 8 1/3,981 0.000251 9 1/10,000 0.000100 10 1/25,118 0.0000398 11 1/63,095 0.0000158 12 1/158,489 0.00000631 13 1/398,107 0.00000251 14 1/1,000,000 0.00000100 15 1/2,511,886 0.000000398 16 1/6,309,573 0.000000158 17 1/15,848,931 0.000000063 18 1/39,810,717 0.000000025 19 1/100,000,000 0.000000010 The stars in Ursa Minor are a good constellation to determine how faint of a star can be observed. On star maps bright stars are represented with large dots while dimmer stars are represented with smaller dots. The brightness of the stars of Ursa Minor get fainter starting with Polaris at 2.0 magnitude which is located on the right side of the below star maps. The rest of the stars starting from bright to dim are 2.1, 3.1, 4.2, 4.3, 4.4, 5.0, 5.2 and 5.5 magnitude. Also note that Polaris is located in the same place in the sky throughout the year for each observing location.