rotating adjustable slit
Date: 1850-1900
Inventory Number: 2007-1-0530
Classification: Slit
Dimensions:13.4 × 14.5 × 5 cm (5 1/4 × 5 11/16 × 1 15/16 in.)
DescriptionThis is a heavy, darkened brass component designed to be attached over the end of an optical instrument and position a slit or small window. It has several degrees of motion--rotation around the optical axis; left-right across the optical field, and open-and-closed.
The base is semicircular and has four screw holes. It carries a platform that rotates around the perimeter and is secured by a locking screw.
The platform has a circular aperture that mates up with the base. Above the platform and alongside the aperture, there are two opposing brackets that are operated by means of a horizontal precision screw. Adjustment of the screw moves the brackets closer together or further apart. The brackets currently are empty. Presumably they were designed to hold knife edges or plates that would have formed a slit or window over the opening.
The platform carrying the slit components is also adjustable by another precision screw which moves the slit left and right.
The screw heads are knurled.