This apparatus consists of two identical units, each provided with Polaroid disc mounted in a rotatable mount, with aperture of 25mm. Both rotatable mounts have a lever to add rotaon and a pointer which traverses a 75mmdiameter brass silvered scale divided into 360 1. The size is universal and can be fied to any size of collimator and telescope. To fit over the object end of telescope and colimator.
