However, the Yale Observatory traces its history back to being one of the first formal institutions for astronomical observation in the United States, dating to the 1830s.

With this telescope Olmsted and Elias Loomis made the first American sighting of the return of Halley's Comet on 31 August 1835.

The observatory also possessed a 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 solar parallax.

Under the direction 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.

The installation was originally designed for the comfort of the observer who sat at the eyepiece in a warm room at the top of the tower.

The telescope was thus rigidly mounted for photographing the polar region only, for the purpose of investigating the wobbling of the axis of rotation of the Earth and redetermining the constants of precession and nutation.

The Loomis Telescope was moved to Bethany, Connecticut in 1957, to continue monitoring the apparent motion of the axis of the Earth.