Airy's Transit Telescope

Al di la della Luna; Beyond the Moon; Astrophotography; Astrofotografia; Danilo Pivato

	Airy's Transit Circle (ACT) in the Royal Observatory, Greenwich was disigned by George Biddell Airy, and came into use 150 years ago. The transit circle sits in its original mounting, in the Transit Circle Room. It was immediately recognised by astronomers as an instrument of great accuracy. But its importance for everyone dates from a conference held in Washington DC in 1884 to create an international time-zone system. It was agreed that the meridian line marked by the cross-hairs in the Airy Transit Circle eyepiece would indicate 0° longitude and the start of the Universal Day - Lens: 8.1 inch aperture objective glass Focal Length: 11 feet 7 inches Magnification: 195 (180 for the Sun).