SPECTRAL DATA REFERENCE - Annie Jump Cannon
COLORS:        red, orange, yellow, green,   blue,  violet,
nanometers:    >610 590-610 570-590 500-570 450-500 < 450.
CLASS   spectra   color      color_index  eff.temp.  examples
O    He II,He I   blue        -0.3     28,000-50,000  epsilon Ori.
B      He I, H    blue-white  -0.2      9,900-28,000 Rigel,Spica
A         H       white        0.0      7,400-9,900  Vega,Sirius
F      metals,H   yellow-white 0.3      6,000-7,400  Procyon
G    Ca II,metals yellow       0.7      4,900-6,000  Sun, Alpha Cen
K  Ca II, molec.  orange       1.2      3,500-4,900  Arcturus
M TiO, Ca I,molec.orange-red   1.4      2,000-3,500  Betelguese
R       CN,C      orange-red   1.7      3,500-5,400  ...   carbon stars
S     ZrO,molec.  orange-red   1.7      2,000-3,500  R Cyg carbon stars
N        C        red          > 2      1,900-3,500  R Lep carbon stars
PROMINENT SPECTRAL LINES - 1 nm = 10 Angstrom Units
hydrogen          -> 656.3 nm, C    neutral sodium -> 589.3 nm D
neutral Helium    -> 587.6 nm, ...  neutral iron   -> 527.0 nm E
neutral magnesium -> 516.7 nm,517.3, 518.4 b
TiO, cool stars   -> 495.5 nm,      hydrogen       -> 486.1 nm F
ionized He, hot   -> 468.6 nm,      Fe I           -> 438.4 nm d
CH molecule       -> 430.0 nm, G    hydrogen H     -> 434.0 nm ...
neutral Ca I      -> 422.7 nm, g    hydrogen H     -> 410.1 nm h
ionized Ca II     -> 396.8 nm, H    ionized Ca II  -> 393.4 nm K
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