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Jon Greif

Location of Photo:

Siding Springs Observatory, NSW, Australia, remotely from La Jolla, CA, USA

Date/Time of photo:

August 16, 2021, at 9:00 pm AEST.


Planewave 0.5 meter reflecting telescope and imaging system. Processing with Pixinsight 1.8.8


Two narrow band versions of the Swan Nebula, Messier 17, in the constellation Sagittarius. It was discovered by Philippe Loys de Chéseaux in 1745, and catalogued by Charles Messier in 1764. The Swan Nebula is between 5,000 and 6,000 light-years from Earth and spans some 15 light-years in diameter. It is considered one of the brightest and most massive star-forming regions of our galaxy. The data for these images was captured on three consecutive nights last week (bad weather kept intervening), using a remotely accessed iTelescope.net 0.5 meter Planewave reflecting telescope and imaging system at the Siding Springs Observatory in NSW, Australia, a total of 60 minutes, mixed evenly between Hydrogen alpha, Sulfur ii, and Oxygen iii narrow band filters. The image on the right uses Sulfur for red, hydrogen for green and oxygen for blue (the "Hubble Palette", and the image on the left uses hydrogen for both red and green and oxygen for blue.