Dynamical equinox and analytical theory of the Sun

A concept of the dynamical equinox and its relation to the analytical form of the adopted theory of the Sun is discussed. Connection between the FK4 equinox and the dynamical equinox is determined by comparing two analytical theories of the Sun (the adopted Newcomb's theory and a new one (AT-1) constructed at the Institute of Theoretical Astronomy) with solar meridian observations made at the U.S. Naval Observatory (1911–1971). Corrections to the FK4 right ascensions, ₀ to declinations and to the angle between the equator and the ecliptic are:Secular variations in and are negligible. Large secular variations of ₀ may be explained by improvement of observational conditions after the reconstruction of the telescope pavilion in the forties.Proceedings of the Conference on Analytical Methods and Ephemerides: Theory and Observations of the Moon and Planets. Facultés universitaires Notre Dame de la Paix Namur, Belgium, 28–31 July, 1980.