William Herschel Telescope
4.2 m
Recorded
ING 4.2-m reflector, Roque de los Muchachos, La Palma.
Photo2pemCC BY-SA 3.0
Western Europe’s largest for years. Altazimuth. 4.2-metre primary. The decimal is the aperture.
What it supports
ING states 4.2-m. Engineered 4.2.
What it does not
Not 42 inches. Not Kepler’s 42 CCDs.
ExactnessExact
Form4.2
Unitmetres
Strengthhard