spare secondary mirror for Gregorian telescope
Date: circa 1763
Inventory Number: 0002b
Classification: Mirror
Subject:
Maker: James Short (1710 - 1768)
User: John Winthrop (1714 - 1779)
User: Samuel Williams (1743 - 1817)
Donor: Nathaniel Sparhawk (1715 - post 1779)
Donor: William Pepperrell Sparhawk (1746 - 1816)
Cultural Region:
Place of Origin:
Dimensions:
mirror assembly: 7.3 x 1.7 x 9.3 cm (2 7/8 x 11/16 x 3 11/16 in.)
box: 9.9 x 4.1 x 8.7 cm (3 7/8 x 1 5/8 x 3 7/16 in.)
diameter of mirror: 2.4 cm (15/16 in.)
Material:
Description:
This spare secondary mirror is concave and made of speculum metal. It is attached to a brass disk on a stalk that is set at right angles to a base, which is designed to slide in a track inside the telescope tube. There is an upright pin at the end of the slider. Exposed surfaces are painted black, except, of course, the front surface of the mirror.
The tin box has a pressure-fitting lid. The lid has a diagonal-cross ornamentation. The exterior is corroded; the interior is shiny. There are two brass tracks inside the box to secure the spare mirror in place.
This is a spare secondary mirror for the James Short Gregorian reflector of two-foot focal length (0002).
The tin box has a pressure-fitting lid. The lid has a diagonal-cross ornamentation. The exterior is corroded; the interior is shiny. There are two brass tracks inside the box to secure the spare mirror in place.
This is a spare secondary mirror for the James Short Gregorian reflector of two-foot focal length (0002).
In Collection(s)
Signedunsigned
FunctionSpare primary and secondary mirrors were often included with high quality reflecting telescopes in order to change the magnification of the instrument.
Historical AttributesThis spare mirror accompanied the Short telescope that was given to Harvard by Nathaniel Sparhawk, acting as guardian for his son, William Pepperrell.
Professor Winthrop used this telescope and micrometer to observe the Transit of Venus in 1769 from Cambridge.
The telescope is mentioned in several archival documents, including an inventory of 1779 that lists "A reflecting Telescope with a micrometer" and "one cannister containing one reflector for the telescope given by Sir William Pepperell."
Professor Winthrop used this telescope and micrometer to observe the Transit of Venus in 1769 from Cambridge.
The telescope is mentioned in several archival documents, including an inventory of 1779 that lists "A reflecting Telescope with a micrometer" and "one cannister containing one reflector for the telescope given by Sir William Pepperell."
Published ReferencesDavid P. Wheatland, The Apparatus of Science at Harvard, 1765-1800 (Cambridge: Harvard University Press, 1968), 20-21.
