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Jon Greif

Location of Photo:

Borrego Springs, CA, USA

Date/Time of photo:

December 4, 2021, at 11:00 pm PST


Astrotech AT72EDII 72 mm refractor, ZWO ASI533MC Pro imaging camera, Rainbow Astro RST-135 mount, ZWO 30 mm guidescope, ZWO ASI294MM mini guide camera, Ekos capture software and Pixinsight processing software.


The very bright star in the center of this photo is Sadr (AKA Gamma Cygni), the 3rd brightest star in the constellation Cygnus, the Swan, forming the center of an asterism of five stars called the Northern Cross. Sadr is located about 1800 light years from our Sun, but compared to the Sun this is an enormous star, with 12 times the Sun's mass and about 150 times the Sun's radius. It is emitting over 33,000 times as much energy as the Sun. Massive stars such as this consume their nuclear fuel much more rapidly than the Sun, so the estimated age of this star is only about 12 million years old -- the Sun is 4.6 billion years old. Sadr is surrounded by a very pretty display of nebulosity (largely hydrogen gas), which shows up nicely in this photo, which represents 3 hours of integration time (36 300-second subs).