Polarscope Illuminator - EQ3 and EQ5
13/12/2011 - Polymorph formed around the inside of the front aperture with a lip to stop it falling into the mount. The basic circuit is single resistor (470R) driving a white LED (should be red I suppose) from a CR20XX lithium battery via a sub-min switch. Just insert it, use it and remove it - simple and very cheap - only used a few grams of Polymorph. Wouldn't win any prizes for engineering finesse though. Post trial modification - red tape over the LED which was much too intense; now works a treat.