Horse's Head' dark nebula in Orion.
© Science Museum / Science & Society Picture Library
Horse's Head' dark nebula in Orion, 13 November 1920. Glass positive of the dark nebulosity South of Zeta (G) Orionis, taken from Mount Wilson Observatory in California, USA, using a 100 inch reflector telescope with a focal length of 42 feet and an exposure time of three hours. Dimensions: 14 inches x 17 inches.