In order to compute the dispersion relation, lines stored in table
line.tbl have to be cross-identified with a reference catalogue
. For the first few spectral lines in the central row,
this has to be done interactively, the rest is automatic. The sequence:
Midas...> SET/LONG LINCAT= hear.tbl
Midas...> IDENTIFY/LONG
plots the central row of the comparison spectrum 
on
the graphics device and activates the graphic cursor.
The lines are selected by positioning the graphics cursor
on them and clicking the left-hand mouse button or Return.
On the session terminal you will be prompted for the wavelength (to be entered
in the same unit as in 
). The command will search for a
corresponding entry in table line.tbl. If it is found, the wavelength
you enter interactively will be
stored in the column :IDENT of table line.tbl.
An asterisk, `` * '', will delete a previously made identification. To exit,
click the middle mouse button on the graphics device.
At least 2 lines have to be identified interactively, but it
is safer to identify a few more, especially
if the dispersion relation is sensibly non-linear. They should
be evenly distributed over the relevant range in wavelength. The
identifications can be checked with:
Midas...> PLOT/IDENT
which plots the central row of the comparison spectrum and
the interactive line identifications.