- make a copy of your telluric spectrum:
cp telluric.fits telluric_fixed.fits

- splot and remove the telluric features and save:
-O2 from about 6855-6960
-H2O from about 7100-7375
-O2 from about 7580-7680
-H2O from about 8135-8345
-H2O from about 8815-9830
=> result should be a gentle line approximating the slope of the continuum.

- divide the modified spectrum by the fixed spectrum
> sarith telluric.fits / telluric_fixed.fits telluric_mult.fits

- splot telluric_mult.fits and make sure the features are predominantly above one (edit if necessary).

- multiply object spectrum by telluric_mult.fits
> sarith object.fits * telluric_mult.fits object_tellcor.fits