plate holder for 8-inch photographic telescope
Date: 1880-1890
Inventory Number: 1996-1-0471
Classification: Photographic Plate Holder
Dimensions:32.3 × 34.3 × 5.5 cm (12 11/16 × 13 1/2 × 2 3/16 in.)
box: 10.6 × 39.5 × 36.5 cm (4 3/16 × 15 9/16 × 14 3/8 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 (21.3 cm) but it has been squared off to create an opening of 7.75 x 7.75 inches. The outer diameter of the collar is 8 3/4 inches (22.2 cm). There are 4 horizontal screws for tightening the plate holder assembly to the telescope tube. The rear of the plate is damascened.
This plate (A) has a track in which plate B moves 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. A pair of binding posts are mounted adjacent to the screw.
The frame for the glass plate has brass sides, latches, and hinges with a mahogany door. The metal is silvered. There is a silvered clamping lever on the hinge side of the door. 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. The other end of the trough has a brass column in which a light would have been inserted for illumination of the cross hairs. The light is missing and its electrical connectors.
An eyepiece (missing) is mounted on a slider that moves in a track above the glass on the trough.
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. The lid is split and separated from the box bottom.
Various accessories to the plate holder are missing.