  Acquiring data for spectral classification of heavily reddened stars using
traditional criteria in the blue-violet region of the spectrum can be
prohibitively time consuming using small to medium sized telescopes. One such
star is the Vatican Observatory emission-line star VES 735, which we have found
excites the HII region KR140. In order to classify VES 735, we have constructed
an atlas of stellar spectra of O stars in the yellow-green (4800 - 5420 A). We
calibrate spectral type versus the line ratio HeI 4922:HeII 5411, showing that
this ratio should be useful for the classification of heavily reddened O stars
associated with HII regions.
  Application to VES 735 shows that the spectral type is O8.5. The absolute
magnitude suggests luminosity class V. Comparison of the rateof emission of
ionizing photons and the bolometric luminosity of VES 735, inferred from radio
and infrared measurements of the KR 140 region, to recent stellar models gives
consistent evidence for a main sequence star of mass 25 M_sun and age less than
a few million years with a covering factor 0.4 - 0.5 by the nebular material.
  Spectra taken in the red (6500 - 6700 A) show that the stellar H-alpha
emission is double-peaked about the systemic velocity and slightly variable.
H-beta is in absorption, so that the emission-line classification is ``(e)''.
However, unlike the case of the more well known O(e) star Zeta Oph, the
emission from VES 735 appears to be long-lived rather than episodic.
