Great refractors were often used for observing double stars and equipped with a Filar micrometer. Gilbert "Gil" Paul Filar (born June 8, 1986) is a Canadian writer, ex-actor and -magician. The verb "Filar" in Portuguese literally means "hold, arrest, grab". Instruments such as a filar micrometer could be attached to the telescope. The precursor to the filar micrometer was the micrometer eyepiece, invented by William Gascoigne. In Portuguese the verb "filar" means "to grasp strongly with the teeth". However, filar eyepieces are still used in teaching astronomy and by some amateur astronomers. Filar was imprisoned during World War II in seven different Nazi concentration camps. Filar died in Wyncote, Pennsylvania on July 10, 2012, aged 94.