Atlas of spectra in the 6485–6510 Å region, containing the “quintet” of strong Ca I, Fe I, and Ba II lines. These and other prominent lines are indicated near the bottom axis. Normalized, telluric-line corrected spectra for MS stars are shown in black, in a temperature sequence (hotter to the bottom), and offset by 0.5 units for clarity. Red spectra are for giant stars at similar temperatures as the respective MS spectra. Gravity-sensitive lines stand out clearly from the comparison. Spectral ranges used to compute the β_t index are indicated with cyan color (and the enclosed yellow range), while green ranges indicate the index reference continuum. Yellow ranges are instead used to compute the β_c index, with the same reference continuum as for β_t.