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Spectroscopic Atlas for Amateur Astronomers 16
3.5 Normalisation of the Intensity
An absolute flux calibration of the intensity profile would be very time con-
suming and is not necessary for the purpose of this atlas. But the contin-
uum intensity of the rectified profiles was always normalised to unity, so
that the medium continuum level yields about ܫ = 1. An absorption line is
usually saturated to the maximum if it reaches from the continuum level
down to the wavelength axis ܫ = 0. At the applied low to medium resolu-
tions, in stellar spectra this can rarely, if at all, be seen. Hence, for space
saving reasons, in most of the cases, not the entire range of saturation is
presented. Instead the corresponding level on the wavelength axis is indi-
cated with amounts mainly in a range of 0.3–0.6. In case of montages
showing several spectra in one chart, the single profiles have been normal-
ised to unity, based on the same continuum section, to enable a rough
comparison of the line intensities.
3.6 Line Identification
For the sometimes complex identification process of spectral lines nearly all referenced in-
formation sources have been used. Some intensive, but in all the listed sources not docu-
mented lines, have been determined with Vspec (Tools/Elements/line ident). The values,
implemented in this tool, are based on the ILLSS Catalogue, Coluzzi 1993. This procedure
was applied very restrictively, i.e. in few cases with a clear profile, high line intensity and
missing, plausible alternative elements in the immediate neighbourhood. The labelling of
such items is declared with a red "V".
The wavelengths of spectral lines are here usually labelled with an accuracy of two decimal
places. These values were complemented from the Vspec tool, because in ancient sources
(e.g. BSA), the indicated accuracy is only rounded to 1 Å. All labelling, lacking decimal
places, here mostly indicate, that the line is a “blend”, formed by several elements/ions
with comparable intensity. Typically affected are metal absorption lines in spectra of the
middle to late spectral classes. However, if in such cases the intensity of a blended line is
clearly dominated by a certain element or ion it’s also used to label the whole blend.
3.7 Presentation
All spectra are at least documented by a broadband profile (200L grating). In the presence
of interesting lines or according information, higher resolved spectra are attached, re-
corded with the 900L grating ore in some special cases even with the SQUES Echelle spec-
trograph [600]. The line profiles are supplemented on the wavelength axis by synthetically
produced 1D-spectra (Vspec). Their colour gradient shall chiefly serve as a rough visual ref-
erence for the wavelength domain.
Generally, only such details are commented, which are really recognizable in the profiles.
Molecular absorption bands are marked with this icon: .
For densely labelled tables, I recommend to zoom it on the screen – even if inaccuracies of
my drawings become relentlessly obvious this way. Due to this "online aspect", I avoided to
separate the tables and the explanatory text in to different parts of the atlas. Due to numer-
ous slim lines, hardcopies of this document require a high printer resolution.
