During the Skylab I, II and III missions, ultraviolet spectra were obtained in 188 fields with a. 15 cm aperture objective-prism spectrograph. The instrument has been described by Henize, Wray, Parsons, Benedict, Bruhweiler, Rybski and O’Callaghan (1975; hereafter referred to as Paper I).
The spectra cover the wavelength region from 1300 to 5000 Å and have a resolution of 2 Å at 1400 Å and 12 Å at 2000 Å. Absorption and/or emission lines of C II λ 1335, Si IV λ 1394, 1403 and C IV λ 1549 are visible in more than one hundred stars. The lines of Si IV and C IV are found to be particularly sensitive to stellar temperature and luminosity. Since these lines are visible in spectra of moderate to low resolution it is clear that they should be of special interest in any UV classification system for faint stars. This paper investigates the correlation of the intensities of the C IV and Si IV lines with MK spectral type, and presents a preliminary classification scheme for 04 to B2 stars based on these lines.