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Limiting magnitude is used to evaluate the quality of observing conditions. It tells the magnitude of the faintest star visible by naked eye. The limiting magnitude could also be observed by some instrument. It describes well the transparency. As fainter stars are visible, as better the transparency is.
Limiting magnitude is used eg. in meteor and deep sky observations. It can be used also to approximate light pollution.
Other limiting magnitude web pages:
The simplest way to evaluate limiting magnitude is to find suitable stars with known magnitudes from star map and check which of them are visible. More clever way is to calculate visible stars inside known star squares and tringles including the corner stars. This method is originally invented by meteor observers.
Area Corner stars Constellation 1 Chi-Zeta-Delta-Xi Dra Draco 2 Beta-Delta-Zeta Per Perseus 3 23-Theta-Beta UMa Ursa Major 4 Alpha-Epsilon-Beta Gem Gemini 5 Tseta-Gamma-Delta Aql Aquila 6 Alpha And - Gamma-Alpha Peg Pegasus-Andromeda 7 Alpha-Beta-Delta Cep Cepheus 8 Alpha-Beta-Zeta Tau Taurus 9 Alpha-Beta-Gamma-Delta Leo Leo 10 Alpha-Zeta-Gamma Vir Virgo 11 Alpha CrB - Gamma-Alpha Boo Corona Borealis-Bootes 12 Alpha Ser - Beta Lib - Delta Oph Serpens-Libra-Ophiuchus 13 Beta-Zeta Lyr - Theta-Nu Her Lyra-Hercules 14 Epsilon-Eta-Gamma Cyg Cygnus 15 Beta Dra - Tau-Pi Her Draco-Hercules 16 Alpha CVn - Epsilon-Eta UMa Canes Venatici-Ursa Major 17 Epsilon-Theta-Delta Aur Auriga 18 Mu-Gamma-Phi And Andromeda 19 Kappa-Alpha Dra - Beta UMi Draco-Ursa Minor 20 42-Beta-Gamma Cam Camelopardalis
In observations the area should choose so, that it is either near the view direction or zenith, depending on observations and the situation. Meteor observers use the viewing direction. Deep sky observers (In Finland) use the area in 45 degrees altitude.
These pages are maintained by:
Veikko Mäkelä, Veikko.Makela@ursa.fi
Mika Pirttivaara, Mika.Pirttivaara@ursa.fi