filar micrometer
Date: circa 1885
Inventory Number: 1996-1-0028
Classification: Micrometer
Subject:
Maker: Fauth & Company (1874 - 1905)
User: Harvard College Observatory (founded 1839)
Owner: Donald H. Menzel (1901 - 1976)
Cultural Region:
Place of Origin:
Dimensions:
micrometer: 6.7 × 24 × 12.6 cm (2 5/8 × 9 7/16 × 4 15/16 in.)
box: 11.3 × 27.7 × 23.3 cm (4 7/16 × 10 7/8 × 9 3/16 in.)
Accessories: spare parts, wood case
DescriptionThis filar micrometer is designed to screw onto a telescope with an opening of 2 1/2 inches. The micrometer is made of red brass with a silvered scale. The scale has a vernier and reads to 1 minute of arc. Rotation of the micrometer head with respect to this scale is done by a small gear operating on the geared rim of the circular base. A thumbscrew attached to the gear has a hard rubber knurled head.
A steel screw with a knurled knob of hard rubber at each end moves the lower part of the micrometer longitudinally in a track. A screw on the left side of the slider with the eyepiece moves it in another track. This screw also has a hard rubber knob, but it is shaped like a octagonal tubular bead. The micrometer drum on the side is divided into 100 units.
The instrument comes with 2 fittings for lamps to illuminate the cross hairs. One is of nickeled brass; the other is of hard rubber. There is a spare eyepiece and two adaptive collars, some rolled up chart paper, a couple of screws, a fitted case padded with dark teal velvet, and a key.
A steel screw with a knurled knob of hard rubber at each end moves the lower part of the micrometer longitudinally in a track. A screw on the left side of the slider with the eyepiece moves it in another track. This screw also has a hard rubber knob, but it is shaped like a octagonal tubular bead. The micrometer drum on the side is divided into 100 units.
The instrument comes with 2 fittings for lamps to illuminate the cross hairs. One is of nickeled brass; the other is of hard rubber. There is a spare eyepiece and two adaptive collars, some rolled up chart paper, a couple of screws, a fitted case padded with dark teal velvet, and a key.
Signedon slider: FAUTH & Co. / WASHN. D. C.
InscribedOn piece of masking tape inside case: DHM PERSONAL / PROPERTY
on label on lid of case: Donald H. Menzel / FILAR MICROMETER
scratched on lid, and barely legible: MICROMETER
on label on lid of case: Donald H. Menzel / FILAR MICROMETER
scratched on lid, and barely legible: MICROMETER
FunctionA filar micrometer of this sort is a precision eyepiece for a telescope in which small separations between objects can be measured. One typical astronomical use would be in observing the separation of double stars.
Historical AttributesThis filar micrometer was owned and used by Donald H. Menzel, director of the Harvard College Observatory from 1952 until 1966.
James Gilbert Baker, the astronomer and optical scientist gave this assessment on June 19, 1973: "To fabricate in Japan with existing instrument as model, $8,000.00. To fabricate in U.S., $12,000.00. To refurbish existing instrument in U.S., $3,000.00. Antique Value, as is, $5,000.00."
James Gilbert Baker, the astronomer and optical scientist gave this assessment on June 19, 1973: "To fabricate in Japan with existing instrument as model, $8,000.00. To fabricate in U.S., $12,000.00. To refurbish existing instrument in U.S., $3,000.00. Antique Value, as is, $5,000.00."
Curatorial RemarksBoston Globe obituary dated Dec. 15, 1976, found in case and placed in file.
ProvenanceDonald H. Menzel; gift to CHSI, 1973