Black and white photograph with caption for two images of a 12-inch equatorial position micrometer (M-48) front and side views. Micrometer built for Philadelphia High School. The caption reads, "The micrometer is an instrument attached to the eye end of a telescope and is intended for measuring the diameter of sun, moon, and planets, the size of sun spots and markings on the planets; the distance of the satellites from their primaries- between two contiguous stars- between a star and planet or between a comet and a contiguous star in order to determine its motion, etc."