These were Stackpole telescopes of "broken-tube" design with a 2½" clear aperture and 30 inch focal length. The viewing eyepiece was at the far end of the horizontal part, behind the spoked setting circle. The two hooks on the right used to carry an oil lamp for the cross-hair illumination, visible in this picture (12k.jpg).
Publications of the USNO, Second Series, Vol. IV, Part IV, Plate V
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