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8.25-inch meridian circle parts
8.25-inch meridian circle parts

8.25-inch meridian circle parts

Date1868-1870
Inventory NumberHA0112s
ClassificationMeridian Circle
Subject
    Maker Troughton & Simms 1826 - 1923
    User Joseph Winlock 1826 - 1875
    User Harvard College Observatory founded 1839
    User William Augustus Rogers 1832 - 1898
    Cultural Region
      Place of Origin
        Dimensions7.1 x 45.4 x 9.5 cm (2 13/16 x 17 7/8 x 3 3/4 in.)
        Material
          DescriptionBrass components of meridian circle (with its telescope) are stored in several very large wood crates. The crates were used to return the instrument from an exhibition loan to the Adler Planetarium in Chicago.

          General description of the Meridian Circle:

          The meridian circle had an objective of 8.25-inch aperture and a focal length of 9' 4.4". (CHSI inv. HA0112e) The aperture of each collimator was 8 inches, and the focal length the same as the main telescope. (see CHSI inv. 2006-1-0051 for the collimator tailpieces.)

          The telescope was tapered for strength, with the middle section being a cube into which each half was fitted. The axis consisted of truncated columns attached to the cube at at right angles from the telescope. The length of the axis was 4 feet. The pivots were 3.58 inches in diameter. The third pair of opposing sides of the cube was pierced with 8-inch apertures in the line of sight of the collimators when the telescope was placed in a vertical position.

          The diameter of each graduated circle was 3 feet. The circles were graduated to every 1/5 minute of arc and could be read to fractions of a second by means of reading microscopes equipped with micrometers.

          The pivots, microscopes, and graduated circles were protected from dust by glass cases.
          Signedunsigned
          FunctionThe meridian circle is the primary, foundational instrument of an observatory. It is used to determine the right ascensions and declinations of celestial bodies.
          ProvenanceHarvard College Observatory
          Historical AttributesOne of the first efforts of Joseph Winlock, the director of the Harvard College Observatory from 1866 until 1875, was to replace the old Troughton & Simms transit circle with a larger, state-of-the-art meridian circle. Winlock called the new meridian circle his "first and most pressing want." In 1867, the Harvard Corporation let Winlock visit Europe to check out the latest meridian circles there. In March 1868, he began negotiations with Troughton & Simms, and in May 1868, placed the full order. There were many delays and broken promises by the makers. The meridian circle was not mounted until 1870. It was designed to include a fine 8.25-inch objective made by Alvan Clark & Sons. The ultimate cost for the meridian circle was $13,385. Most of the money was raised by subscription. Steep tariffs also caused problems for the Observatory. The import duty on the meridian circle was $1000 gold. Winlock applied to the U. S. Congress for a special act of exemption.
          8.25-inch meridian circle parts
          8.25-inch meridian circle parts
          Troughton & Simms
          Date: 1868-1870
          Object number: HA0112a
          8.25-inch meridian circle parts
          8.25-inch meridian circle parts
          Troughton & Simms
          Date: 1868-1870
          Accessories: Cylindrical piece mounted perpendicular to a triangular base, stored on palette with HA0114a. Cylindrical piece mounted in oval brace with 2 large bolts. Bag of bults and flat wrench.
          Object number: HA0112b
          8.25-inch meridian circle parts
          8.25-inch meridian circle parts
          Troughton & Simms
          Date: 1868-1870
          Accessories: Cylindrical piece mounted perpendicular to a triangular base, stored on palette with HA0114a. Cylindrical piece mounted in oval brace with 2 large bolts.
          Object number: HA0112c
          8.25-inch meridian circle parts
          8.25-inch meridian circle parts
          Troughton & Simms
          Date: 1868-1870
          Object number: HA0112d
          8.25-inch meridian circle parts
          8.25-inch meridian circle parts
          Troughton & Simms
          Date: 1868-1870
          Object number: HA0112f
          8.25-inch meridian circle parts
          8.25-inch meridian circle parts
          Troughton & Simms
          Date: 1868-1870
          Object number: HA0112g
          8.25-inch meridian circle parts
          8.25-inch meridian circle parts
          Troughton & Simms
          Date: 1868-1870
          Object number: HA0112h
          8.25-inch meridian circle parts
          8.25-inch meridian circle parts
          Troughton & Simms
          Date: 1868-1870
          Object number: HA0112i
          8.25-inch meridian circle parts
          8.25-inch meridian circle parts
          Troughton & Simms
          Date: 1868-1870
          Object number: HA0112j
          8.25-inch meridian circle parts
          8.25-inch meridian circle parts
          Troughton & Simms
          Date: 1868-1870
          Object number: HA0112k
          8.25-inch meridian circle parts
          8.25-inch meridian circle parts
          Troughton & Simms
          Date: 1868-1870
          Object number: HA0112l
          8.25-inch meridian circle parts
          8.25-inch meridian circle parts
          Troughton & Simms
          Date: 1868-1870
          Object number: HA0112m