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Catalogue and alternative designations Palomar 9, NGC 6717


Type Globular cluster
Position 18 55.1, -22 42
Constellation Sagittarius
Camera and Telescope STXL16200 and 36.8 cm RCOS Ritchey Chretien 
Focal Ratio F9
Exposure Details LRGB image using Astrodon filters.  Luminance = 150 minutes, Red = Green = Blue = 80 minutes. Luminance unbinned, colours binned 2x2.
Description This is the brightest of the 15 globular clusters cataloged by George Abell based on the Palomar Sky survey plates but it was William Herschel who actually discovered this cluster and cataloged it as H III.143. He described it as a very faint round nebula and apparently thought it was a cluster with nebulosity. It was first recognized as globular cluster by Per Collinder in 1931. Abell was unaware of its identity, as it was not previously classified as a globular cluster. Its identification with NGC 6717 was probably done in 1958 by Alter. It's about 23,000 light years distant and quite easy to find being right next to one of the 5th magnitude components of the double star n Sgr