The observatory also possessed an heliometer, ordered from Repsold and Sons by H . A . Newton in 1880, delivered in time for measurements of the Transit of Venus on December 6, 1882 for determination of W . L . Elkin from 1883 to 1910 the heliometer yielded ( according to Frank Schlesinger ) the most ( 238 ) and the best parallaxes obtained before the advent of photographic astrometry.