An observational determination of the principal nutation constants

The longitude and obliquity components of the principal nutation terms were derived from observations made in 1955–1977 of 43 star-pairs common to the ILS Programmes VI and VII. The observations were reduced to a uniform system appropriate to these 43 star-pairs. The results are 6'.'850 for the longitude component and 9'.'212 for the obliquity component.