Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume 4, Declinations -26°.0 to -12°.0.

This is the fourth ofseven volumes in a program of systematic reclassification of the Henry Draper stars on the MK system and contains all HD stars between δ = -26°.0 and -12°.0. The stars were classified visually on objective-prism plates taken with the Michigan Curtis Schmidttelescope at Cerro Tololo Inter-American Observatory. The 4°+6° prisms yield a dispersion at Hγ of 108 Å/mm, and the resolution is about 2 Å/mm, comparable to that of the original MK system. The spectra were taken on IIaO plates and widened to 0.8 mm, with 20^m, 4^m, and 1^m exposures being obtained. Of the 33,301 stars in the catalogue, 32,563 or 98% were classifiable. Previously published types are listed for the 2% not classifiable on the plates. Internal classification errors were obtained using the stars classified independently on more than one plate. Both the internal and external errors are similar to those usually obtained in the classification of slit spectra.