This six inch-diameter, f/15 refracting telescope was built in 1890 by George Clark of the Alvan Clark & Sons company of Cambridge, Massachusetts. The 6-in telescope is regularly used for teaching the Department's introductory astronomy subjects.
Alvan Clark & Sons was the premier American telescope-maker of the late 19th and early 20th centuries, and the Clarks were the first American opticians to equal the quality of the European makers. Alvan Clark & Sons also made the optics of the 30-in telescope at Pulkova Observatory in Russia, the 36-in Lick refractor in California, and the 40-in Yerkes telescope outside Chicago — still the largest refractor ever constructed.
The original owner of the telescope was a Mr. Cartwright, an amateur in Detroit, Michigan who bought it “merely for his pleasure.” He paid $2300, not including the cost of additional accessories. He housed it under an unusual, custom-built dome with three overlapping panels moving vertically, rather than in a more traditional slotted dome such as the one in which it is currently housed at Whitin.
Following Mr. Cartwright's death, the telescope was sold to Wellesley College in 1904 for $850. It found its current home in 1905 when the original Whitin Observatory was doubled in size. The building expansion added the library, the 6-in dome, and a transit telescope room. In the photo below, note the open transit roof hatch to the right of the 6-in dome. (That transit room is now the control room for the 24-in research telescope.)
The telescope received a new mounting in 1923 from the Alvan Clark company, and its dome seems to have been either modified or replaced at about that same time. In the mid-1980s the telescope was extensively overhauled and restored by John Richardson of Needham.