plate holder for 8-inch photographic telescope
Date: 1885-1890
Inventory Number: 1996-1-0469
Classification: Photographic Plate Holder
Dimensions:34 × 33 × 7.5 cm (13 3/8 × 13 × 2 15/16 in.)
box: 12.1 × 38.5 × 38.3 cm (4 3/4 × 15 3/16 × 15 1/16 in.)
DescriptionThis is a plate holder designed to attach to a telescope with an 8-inch aperture. It is formed of three flat, dasmacened red-brass plates (A, B, C) adjustable at right angles to each other plus a mahogany frame for the photographic glass plate. It is also provided with an adjustable cross hairs and eyepiece.
The rear plate (A) of the plate holder has a raised collar that would be inserted into the end of the photographic telescope and serve as its tailpiece. The aperture of the collar (inner diameter) is 8 11/32 inches (21.2 cm). The outer diameter is 8 3/4 inches (22.2 cm). There are three horizontal screws for tightening the plate holder assembly to the telescope tube. The rear of the plate is damascened.
This plate (A) moves in a track attached to another plate (B). The motion is adjusted by means of a large knurled screw. This second plate (B) is attached to another plate (C) that carries the frame for the photographic plate. This C plate is adjusted with respect to the B plate below by means of another large knurled screw. There is a graduated scale on the track for this plate. A pair of binding posts are mounted adjacent to the screw. A bit of green cotton wrapped wire is still present. This is for a small light to illuminate the cross hairs (decribed below).
The frame for the glass plate has metal sides and hinges with a wood door. The metal is silvered. The shutter slide is made of aluminum. A pull knob releases it and permits it to be retracted or slid into place. The glass plates to be used would be about 6.5 x 6.5 inches.
Along side the plate frame there is a metal trough with a glass top. A precision screw within the trough moves a metal bracket longitudinally down the trough. This bracket has a small lens with cross hairs. It's motion is operated by a knurled thumbscrew outside of the trough. A black ribbed cloth ribbon runs down the bottom of the trough and extends outside it below the thumb screw. It has an ivory handle on both ends. (One handle is ripped off and in the box.) The other end of the trough has a brass column topped with two screws at right angles. This is to hold the light for illuminating the cross hairs.
An eyepiece mounted on a slider moves in a track above the glass on the trough. It is stored separately in the box when not in use.
The instrument has a fitted mahogany box lined in places with green felt. The box has brass hardware including a handle on the side, a lock, and latch hooks.
Signedunsigned
Inscribedin black crayon on top of box: PLATE HOLDER
Historical AttributesUsed by Harvard College Observatory on an 8-inch photographic telescope, possibly the Bache telescope (1885), the Boyden telescope (1887), or the Draper telescope (1889). These instruments traveled to Harvard's field stations in Peru and South Africa. All were made by Alvan Clark & Sons, who may have been involved in assembling this plate holder to fit their telescopes. The parts, however, especially the damascened brass, were likely made by a subcontractor.
ProvenanceHarvard College Observatory, Agassiz Station; transfer to CHSI in 1969.