UV_PREVIEW cannot identify lines if there are two few channels. It
will only display the spectra in this case. A minimum of 32 channels is
required, but confused spectra may also prevent a proper line recogni-
tion.
The line detection is based on the current specified velocity. If this
is incorrect, lines may appear shifted and considered as not detected.
PREVIEW%TOLERANCE indicates the matching precision in frequency (default
is 2 MHz).
If variable \sicvar{REDSHIFT} exists, the frequency scale is corrected
for that source Redshift, so that line identification remains possible.
Gildas manager
2023-06-01