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Spectroscopic Atlas for Amateur Astronomers 19

5 The Fraunhofer Lines

Fraunhofer has characterised the more prominent of Line Element Wavelength [Å]
the solar absorption lines with the letters A to K – ident.
this at a time when the physical relationships were A – Band O2 7594 - 7621
still unknown. Later, additional lines were supple- B – Band O2 6867 - 6884
mented with small letters. These line designations C H (α) 6563
are still in use even in current professional papers. a – Band O2 6276 - 6287
D 1, 2 Na 5896 & 5890
In this atlas some of the Fraunhofer lines are la- E Fe 5270
belled in the solar spectrum and neighbouring spec- b 1, 2, 3 Mg 5184/73/69
tral classes. The table shows the listed Fraunhofer F H (β) 4861
lines, rounded to 1 Å (Sources: Table: NASA, d Fe 4668
Graphic: Wikipedia). e Fe 4384
f H (γ) 4340
G – Band CH 4300 - 4310
g Ca 4227
h H (δ) 4102
H Ca II 3968
K Ca II 3934

Below: Original drawing of the solar spectrum by Joseph Fraunhofer. In contrast, the con-
vention today requires the blue region of the spectrum to be left and vice versa the red to
be right. Stunningly visionary appears to me the sketched, estimated intensity profile of the
pseudo-continuum above the 1D-spectral stripe! This type of plotted profiles, today of
course normalised/calibrated and overprinted with the spectral lines, we can find again in
publications only since about the last 40 years!