Photograph of a pastel drawing of the Omega Nebula (M17) from observations by Prof. E.S. Holden and M. Etienne Leopold Trouvelot (artist), dated September 1875, using telescopes of the United States Naval Observatory at Foggy Bottom, Washington, DC.

Photograph showing a pastel drawing of the Omega Nebula, a feature often today called the Swan Nebula. Etienne Leopold Trouvelot (1827-1895), a French artist and the astronomer, Prof. E.S. Holden (1846-1914), together produced this sketch in 1875. It is based on observations made at the United States Observatory at Foggy Bottom in Washington using the 26-inch Clarke refracting telescope. Visible in small telescopes, the nebula was first recorded being observed in 1745-6 by Frenchman, Philippe Loys de Cheseaux. Located in the Milky Way, it consists of a large glowing cloud of hydrogen gas.