In early 1793 Thomas Jefferson (when serving as the First Secretary of State for President George Washington) acquired the most valuable scientific instrument in his collection, an equatorial telescope by Jesse Ramsden (1735-1800), whom he considered preeminent among makers. Jefferson purchased the instrument from his friend David Rittenhouse, who was selling the instrument on consignment for the original owner, John William Gerard de Brahm. De Brahm had been the King's Surveyor General for the Southern District of America prior to the Revolutionary War.

With "this noble instrument," as he called it, Jefferson fixed the meridian at Monticello and viewed the solar eclipse of 1811 (with James Madison likely at his side using a Dollond Telescope). The Equatorial could also be used to determine both latitude and longitude. Judged by one scholar to be "unquestionably the most sophisticated instrument in the United States" at the time, Jefferson's equatorial was the foundation of his favorite theory of a method for determining longitude by lunar distances without a timepiece. Jefferson urged Lewis & Clark to take this instrument with them to explore the Louisiana Purchase and the Pacific Northwest, but they declined, thinking the instrument was too fragile for the rugged trip.

Jefferson's Equatorial Telescope has been missing for 200 years.

Longtime scientific instrument dealer and collector Dale Beeks surfaced this Equatorial Telescope shortly before he passed away. Dale and I started researching this instrument together as soon he acquired it. Sensing that this might be Jefferson's missing Equatorial, I wanted to finish the job and now own the instrument.

Interestingly, the Equatorial has no markings on it whatsoever that would identify who made or owned it. Notwithstanding the lack of the makers name on the instrument, I am 100% certain that Jesse Ramsden made this instrument, or, more precisely, the workers in his shop made it under Ramsden's supervision.

A more interesting question - is this Thomas Jefferson's missing Equatorial? While TJ did not engrave his initials on the instrument or carve his initials on the original box, ALL the evidence suggests that Thomas Jefferson did in fact own this instrument. The evidence shows Jefferson purchased a 7 inch (the diameter of the circles and arcs) Ramsden Equatorial made between 1771 and 1774 from John William Gerard de Brahm, and that Jefferson added a second telescope, a Watch Telescope, to his Equatorial. The Equatorial pictured above is a 7 inch Equatorial made between 1771 and 1774 with a Watch Telescope on it. One KEY additional fact - Ramsden only made a handful of Equatorials (which were of different sizes) between 1771 and 1774. Another KEY additional fact - adding a Watch Telescope to an early Equatorial wasn't a thing. The makers didn't offer to include a Watch Telescope, and the contemporaneous commentators never mentioned the need for adding a Watch Telescope . I therefore believe there is almost no chance that there is a SECOND 7 inch Ramsden Equatorial made between 1771 and 1774 with an added Watch Telescope.

So, I conclude that it's EXTREMELY LIKELY that Jefferson owned my Equatorial.