Essentially all spectra reproduced in this Atlas were obtained
with the CARELEC spectrograph (Lemaître et al. 1990) mounted
on the 193 cm telescope of the OHP observatory. Nine spectra
(Figs. 20 (click here) and 21 (click here)) were obtained with the AURELIE spectrograph
(Gillet et al. 1994) mounted on the 152 cm telescope of the
OHP. The dispersion of 33 Å/mm is the same in both cases and
leads, with the receivers used (CCD Thomson or Tektronix), to
a resolution of the order of 2 Å.
The reduction of the observations was made at the OHP with the
IHAP program. The images are treated first to eliminate the
observational noise (subtraction of an off-set field) and to
eliminate the defects of the receiver (division of the spectrum
by a flat field given by a tungsten lamp).
The spectra were then calibrated in wavelength, using a Ne lamp
as calibration source. Next the spectra are straightened and
normalised to the continuun, and finally plotted with an HP
tracer. Each spectrum is thus an intensity tracing as a
function of wavelength, the intensity of the continuun always
being set equal to unity.