tailpiece micrometers for collimators of the 8.25-inch meridian circle
Date: 1868-1870
Inventory Number: 2006-1-0051
Classification: Micrometer
Maker: Troughton & Simms ? (1826 - 1923)
Maker: Alvan Clark and Sons ? (1846 - 1958)
Attributed to: William Augustus Rogers (rulings) (1832 - 1898)
User: William Augustus Rogers (1832 - 1898)
User: Joseph Winlock (1826 - 1875)
User: Oak Ridge Station (1931 - 2005)
User: George R. Agassiz Station, Harvard (1951 - 1982)
User: Harvard College Observatory (founded 1839)
Cultural Region:
Place of Origin:
Dimensions:
tailpiece "a": 10.8 x 13.2 x 6.7 cm (4 1/4 x 5 3/16 x 2 5/8 in.)
tailpiece "b": 10.9 x 13 x 6.7 cm (4 5/16 x 5 1/8 x 2 5/8 in.)
box: 12 × 18 × 28 cm (4 3/4 × 7 1/16 × 11 in.)
Description2006-1-0051 consists of two nearly identical tailpiece micrometers ("a" and "b") from the two collimating telescopes of the 8.25-inch Meridian Circle of Harvard College Observatory.
Each tailpiece consists of a cylinder of brass with external threads at the bottom. The external diameter is 10 cm. The cylinder is topped with parallel plates and a brass carriage that moves to and fro by means of a micrometer screw. The screw has a drum that is silvered and graduated from 0-100 every 1. The edge profile of each tailpiece is circular but they are truncated differently. The edge of tailpiece "a" is truncated at right angles to the micrometer carriage. The edge of tailpiece "b" is truncated in direct line with the carriage.
The carriage is pierced in the center with a circular aperture (7/8 inch, 2.1 cm in diameter). Holes on the carriage and plate show that some micrometer mechanism was removed.
A glass slide is glued over the opening on each one. These slides are divided with very fine pairs of lines. Tailpiece "b" has many more lines than tailpiece "a."
The tailpiece micrometers are stored together in a wood box. They are cushioned by batting of cotton threads, brown paper, and tissue paper.
The lid of the box is marked in red marker with a diagram of the tailpiece showing the positions of the rulings and micrometer drum and various dimensions. These markings are modern.
Each tailpiece consists of a cylinder of brass with external threads at the bottom. The external diameter is 10 cm. The cylinder is topped with parallel plates and a brass carriage that moves to and fro by means of a micrometer screw. The screw has a drum that is silvered and graduated from 0-100 every 1. The edge profile of each tailpiece is circular but they are truncated differently. The edge of tailpiece "a" is truncated at right angles to the micrometer carriage. The edge of tailpiece "b" is truncated in direct line with the carriage.
The carriage is pierced in the center with a circular aperture (7/8 inch, 2.1 cm in diameter). Holes on the carriage and plate show that some micrometer mechanism was removed.
A glass slide is glued over the opening on each one. These slides are divided with very fine pairs of lines. Tailpiece "b" has many more lines than tailpiece "a."
The tailpiece micrometers are stored together in a wood box. They are cushioned by batting of cotton threads, brown paper, and tissue paper.
The lid of the box is marked in red marker with a diagram of the tailpiece showing the positions of the rulings and micrometer drum and various dimensions. These markings are modern.
Signedunsigned
Inscribedin brown ink on paper label on side of box: Tail Piece Micrometers / from Collimators of / 8-in Meridian Circle. / Complete with reticules..
stamped on label : Dec 28 1931.
on box lid in red marker: [sketch of one of the micrometers]
stamped on label : Dec 28 1931.
on box lid in red marker: [sketch of one of the micrometers]
FunctionThe collimators for the 8.25-inch meridian circle were used to check the alignment of the meridian telescope with respect to the graduated circles. These micrometers were part of the collimating telescopes.
Historical AttributesThe lenses for the collimators were made by Alvan Clark & Sons, who may have made these tailpiece micrometers as well. Another possibility for the maker of the micrometers is Troughton & Simms who made the rest of the meridian circle. The use of fine pairs of lines etched or ruled on glass slides appears to be the work of the principal user of the meridian circle, W. A. Rogers, who experimented with fine rulings on glass for precision optical purposes.
The micrometers were used with the large Meridian Circle at the Harvard College Observatory. When the instrument was lent to the Adler Planetarium for its opening exhibition in 1930 and display during the Century of Progress World's Fair in 1933, the Observatory retained the micrometers for use with other instruments. In fact, they were never used, but languished in a storage cabinet at Oak Ridge Station.
The micrometers were used with the large Meridian Circle at the Harvard College Observatory. When the instrument was lent to the Adler Planetarium for its opening exhibition in 1930 and display during the Century of Progress World's Fair in 1933, the Observatory retained the micrometers for use with other instruments. In fact, they were never used, but languished in a storage cabinet at Oak Ridge Station.
Curatorial RemarksRecovered and brought back to CHSI on August 18, 2005 by Sara Schechner from Oak Ridge Observatory, Harvard, Mass.
ProvenanceHarvard College Observatory, Cambridge, MA, 1868; transferred to Oak Ridge Station, Harvard, MA, circa 1931; transferred to CHSI, 2005.
