  The Ground-based Observational Support of the Fermi Gamma-ray Space Telescope
is conducted by the University of Arizona using the 2.3m Bok and 1.54m Kuiper
telescopes operated by the Steward Observatory (SO). This program monitors
blazar sources with spectroscopic (among others) observations. Yet, the
instrumental broadenings for the different slit widths used in the spectra, are
unavailable (the widths range from 2.0 to 12.7 arcsec). Using
quasi-simultaneous spectroscopic observations of the blazar 3C 273 between the
SO, Observatorio Astrof\'isico Guillermo Haro (OAGH), and Observatorio
Astron\'omico Nacional San Pedro M\'artir (OAN-SPM), we can provide an
estimation of the instrumental profile for two of the slit widths. Since the
instrumental broadening and the slit width are directly proportional, we were
able to estimate the instrumental broadening for all six slit widths used at
the SO. We found significant variations between the instrumental profiles,
emphasizing the need to correct the instrumental broadening for each aperture.
