Methods for the Determination of Lunisolar Precession From Observations of Extragalactic Radio Sources

Although it is not practicable at present to determine the position or motion of the equinox using radio techniques, lunisolar precession may be determined from measurements at two epochs of differences of (i) Right Ascension—RA, and (ii) Declinations—Dec., of extragalactic radio sources. The determinations are largely free from systematic errors, and the magnitudes of random errors, arising principally from tropospheric irregularities, are given for observations with the Cambridge 5-km telescope. Some first epoch measurements have been made with this instrument and it is estimated that by carrying out second epoch measurements after an interval of 5 yr, the centennial value of lunisolar precession will be determined with a standard error of $$\pm\,{0}^{\prime{}\prime}\cdot25$$.