It consists of 50 cm diameter
white painted disc marked at every 5 degree with cross lines at 90° and a
center mark on a stable cast iron base. The main disc and the lamp house
with 12 volt, 24 watt bulb can be rotated and held in any desired position
with the lamp house a Rota table disc with single, double, triple and
quadruple slit and with adjustable lens carries with lens is provided. This
assembly is mounted on a rotatable arm, counterpoised by a heavy weight.