NGC 6946 LRHaGB: stack 27 hrs (L 45x900"+13x1200" and 18x600" each RGB - Ha 20x900s) calibrated and stacked and processed in Pixinsight and CS6, the halpha composition with LRGB data is made by Matteo Collina with a new pixinsight technique.
NGC 6946 (also tentatively known as the Fireworks Galaxy) is an intermediate spiral galaxy about 22 million light-years away, in the constellations Cepheus and Cygnus. In the Catalogue of Named Galaxies, it is called 'Pyrobolus Cygni', or the "Fireworks Galaxy", because of the record number of supernovae discovered in it. It was discovered by William Herschel on 9 September 1798. NGC 6946 is highly obscured by interstellar matter of the Milky Way galaxy, as it is quite close to the galactic plane. The true diameter of the galaxy is approximately 40,000 light-years or just about one-third of the Milky Way's size. In the past century, ten supernovae have been observed to explode in the arms of this galaxy, which has been classified as a starburst galaxy. Chandra Space Telescope observations have, in fact, revealed three of the oldest supernovae ever detected in X-rays, giving more credence to its nickname.
Ten supernovae have been observed in NGC 6946 in the last 100 years: SN 1917A, SN 1939C, SN 1948B, SN 1968D, SN 1969P, SN 1980K, SN 2002hh, SN 2004et, SN 2008S, and SN 2017ea. This makes it the most prolific known galaxy for this type of event over a period of 100 years. By comparison, the Milky Way galaxy, which has double the number of stars as NGC 6946, averages one supernova event per century. It also contains a failed supernova, potential black hole-forming star N6946-BH1.
Other designations UGC 11597, PGC 65001, Arp 29, Caldwell 12