secondary mirrors for Gregorian telescope
Date: circa 1767
Inventory Number: 0001b
Classification: Mirror
Maker: James Short (1710 - 1768)
Maker: Thomas Short (1711 - 1788)
Supplier: Benjamin Franklin (1706 - 1790)
User: John Winthrop (1714 - 1779)
Repaired by: W. & S. Jones (fl. 1791 - 1859)
Cultural Region:
Place of Origin:
Dimensions:
one secondary mirror: 12.6 x 6.5 x 10.8 cm (4 15/16 x 2 9/16 x 4 1/4 in.)
box: 12.1 x 8 x 14.3 cm (4 3/4 x 3 1/8 x 5 5/8 in.)
Material:
Bibliography:
The Apparatus of Science at Harvard, 1765-1800
Description:
A tin box with a hinged lid has a corroded exterior and shiny interior. It has two sets of copper tracks on opposite sides of the box. These are designed to hold two secondary mirrors for the four-foot Short telescope (0001a).
Each mirror is concave and made of speculum metal, which has been attached to a brass disk on a stalk that is attached to a brass base. The base has four slits and serves as a slider in the tracks. The metal fittings to be exposed in the tube are painted black, except for the mirrors' front surfaces. Three, brass, fine-adjustment screws are on the backside of each mirror for collimation.
One secondary is currently inside the tube of 0001a. The one in the box has a diameter of 2.8 cm.
Each mirror is concave and made of speculum metal, which has been attached to a brass disk on a stalk that is attached to a brass base. The base has four slits and serves as a slider in the tracks. The metal fittings to be exposed in the tube are painted black, except for the mirrors' front surfaces. Three, brass, fine-adjustment screws are on the backside of each mirror for collimation.
One secondary is currently inside the tube of 0001a. The one in the box has a diameter of 2.8 cm.
In Collection(s)
Signedunsigned
Historical AttributesThis large brass Gregorian telescope has a four-foot focus. The end of the barrel is engraved 9 = 48, indicating that it was only the ninth telescope with this focal length made by James Short, who died before the mirror could be mounted.
The telescope was acquired with the help of Benjamin Franklin, who visited Short's workshop to supervise the progress of the construction. Franklin told Winthrop by letter (2 July 1767) that Short had "finished the material parts that required his own hand" before he died, but the telescope needed "something about the mounting, that was to have been done by another workman." Thomas Short, James's brother, saw to the completion of the instrument. The bill for the remarkable instrument was 100 guineas.
Winthrop kept this telescope at his house, and used it for the Transit of Venus in 1769.
Repairs were necessary by the early 19th century, and these were undertaken in London by W. & S. Jones. They left the primary mirror untouched, explaining that "the figure is very good like all of James Short's." They did supply "a new stand upon an improved principle in brass, with mahogany folding legs, graduated circle and arch, etc., etc.; cleaning and repairing the brass work of the tube, finder, eye piece, etc.; new japaning the tube, cleaning and adjusting speculums of a Short's 5 [sic] feet Reflector 7 inches aperture, with deal case for eye pieces and speculums." They charged £54.12.0.
The College protested. So, on 19 August 1817, William Jones made this case: "Short's telescope was charged originally [at] more than 100 guineas, [yet] his stand was unmechanical or ill contrived....[The new stand] is very material and [a] most expensive part of the instrument, and we are confident in declaring the value of the Telescope at present is 150 pounds, whereas in the state sent to us for practical & steady use, an Astronomer would not have given 50 shillings. The price of our 4 feet, so mounted is 100 guineas."
The telescope was acquired with the help of Benjamin Franklin, who visited Short's workshop to supervise the progress of the construction. Franklin told Winthrop by letter (2 July 1767) that Short had "finished the material parts that required his own hand" before he died, but the telescope needed "something about the mounting, that was to have been done by another workman." Thomas Short, James's brother, saw to the completion of the instrument. The bill for the remarkable instrument was 100 guineas.
Winthrop kept this telescope at his house, and used it for the Transit of Venus in 1769.
Repairs were necessary by the early 19th century, and these were undertaken in London by W. & S. Jones. They left the primary mirror untouched, explaining that "the figure is very good like all of James Short's." They did supply "a new stand upon an improved principle in brass, with mahogany folding legs, graduated circle and arch, etc., etc.; cleaning and repairing the brass work of the tube, finder, eye piece, etc.; new japaning the tube, cleaning and adjusting speculums of a Short's 5 [sic] feet Reflector 7 inches aperture, with deal case for eye pieces and speculums." They charged £54.12.0.
The College protested. So, on 19 August 1817, William Jones made this case: "Short's telescope was charged originally [at] more than 100 guineas, [yet] his stand was unmechanical or ill contrived....[The new stand] is very material and [a] most expensive part of the instrument, and we are confident in declaring the value of the Telescope at present is 150 pounds, whereas in the state sent to us for practical & steady use, an Astronomer would not have given 50 shillings. The price of our 4 feet, so mounted is 100 guineas."
Published ReferencesDavid P. Wheatland, The Apparatus of Science at Harvard, 1765-1800 (Cambridge: Harvard University Press, 1968), 17-19.
Rolf Willach, "List of Extant Reflecting Telescopes Made by James Short," i>Journal of the Antique Telescope Society, no. 29 (Fall 2007): 11-22, no. 186.
