function fiss_tell_lines,  wv
;+
;  Name: FISS_TELL_LINES
;  Purpose:
;              Yields the optical depth profile of telluric lines
;  Calling sequence:
;             Tau = fiss_tell_lines(wv)
;  Inputs
;           wv      array of wavelengths in angstrom
;  Output:
;          Tau     array of optical thickness
; History:
;      2010 Septmeber: J. Chae first coded
;-


if  abs(median(wv)-6562.8) le 3. then line='H_I_6563'
if abs(median(wv)-8542.) le 8. then line='Ca_II_8542'

case line of
   'H_I_6563':  begin            ; H alpha

;halpha_flux, wl1,  flux1, tr=tr,  fwhm=0.06
;tr1=interpol(tr, wl1, wv-6562.817)
;tau=-alog(tr1)
;return, tau
wvcen=[64.206+0.003, 64.061+0.00, 63.521, 62.44+0.007, 61.097+0.020, 60.555-0.046, 59.813-0.01, 58.65-0.012, 58.149+0.015, $
                            65.545-0.020, 66.55+0.017 ]+6500.D0
wvdop=replicate(0.014, n_elements(wvcen))
adamp=replicate(2.6, n_elements(wvcen))
tau0=[0.30,0.08, 0.09, 0.04, 0.08,0.15,0.015, 0.03,  0.11, $
                               0.033, 0.025  ]
                        end
    'Ca_II_8542': begin
;            wvs=               [36.165,  36.45, 36.68,  38.0152,  38.25,  39.888, 40.817,  42.089,   46.222]+8500.D0
;            ews=                 [58.,        3.,        3.,         31.,        2.,          3.5,        8.,           3670.,   5. ]
;            elms=                ['Si I',      '' ,        '',         'Fe I',     'CN',      'H2O',    'H2O',     'Ca II', 'H2O']
;            ref=                 ['NIST',  'utrecht',  ' ',   'NAVE', 'utrecht',    'utecht', 'NSRD', 'utrecht']
;
caii8542_flux, wl1,  flux1, tr=tr,  fwhm=0.06
;tr1=interpol(tr, wl1, wv-8542.089)
;tau=-alog(tr1)
;return, tau

           wvcen=8500.d0+ [36.45, 36.68,  39.888,  40.817, 46.2222] ;+[-0.07, -0.07, -0.06,-0.065, 0.03]
            wvdop=replicate( 0.028, n_elements(wvcen))
            adamp=replicate(2.6, n_elements(wvcen))
            tau0=[0.030, 0.030, 0.06, 0.17,  0.06]
       end
else     : begin
             wvcen=median(wv)
             tau0=0.
             adamp=0.
             wvdop=0.1
            end
 endcase
nline=n_elements(wvcen)
tau=0.
for line=0, nline-1 do begin
u=(wv-wvcen[line])/wvdop[line]
tau=tau+tau0[line]*voigt(adamp[line],u)/voigt(adamp[line],0)
endfor

return, tau
end