Precession and Galactic Rotation on the Basis of Various Proper Motion Systems

Abstract

Previous determinations of precession on the basis of proper motions resulted in corrections to Newcomb’s value of lunisolar precession in the interval + 0″.75 ≤ Δp ₁ ≤ + 1″.50 per century. From a compilation of several determinations and their reduction to the average of the systems of FK3 and N30 Morgan and Oort (1951) obtained:

$$ \Delta {{\text{P}}_1} = + 0''.75, \,{\text{P}} = \frac{\text{A}}{{4 \cdot 74}} = + 0''.43,{\text{Q}} = \frac{\text{B}}{{4 \cdot 74}} = - 0.''15 $$

per century, where A and B are Oort’s constants. Values in the system of FK4 were derived by Bošniakovich (1965), who applied differential corrections to previous results on the basis of the systematic differences FK4-FK3.