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Fireworks galaxy

Submitter: Albert van Duin
Description: NGC 6946, (also known as the Fireworks Galaxy, Arp 29, and Caldwell 12), is an intermediate spiral galaxy about 22.5 million light-years from us, in the constellations Cepheus and Cygnus. It was discovered by William Herschel on September 9, 1798. NGC 6946 is somewhat obscured by the interstellar matter of the Milky Way galaxy, as it is quite close to the Galactic plane. Nine supernovae (SN 1917A, SN 1939C, SN 1948B, SN 1968D, SN 1969P, SN 1980K, SN 2002hh, SN 2004et, and SN 2008S) have been observed in NGC 6946. This is the largest number seen in any galaxy, hence the name Fireworks Galaxy.

Because NGC 6946 is seen fairly face on, it is a good object for making nice images. In fact, the 'blue and orange' galaxy that is used as a pretty picture in many ASTRON documents is indeed NGC 6946. That image shows the neutral hydrogen as seen by the WSRT (the blue) in combination with the optical image (the orange).

The above image was created by combining 14 luminance, 6 red, 3 green and 3 blue filtered images with an integration time of 600s each. The telescope used is a 400mm F/4.5 reflector.

During imaging, the telescope mount, electrical focuser and autoguider camera were being controlled by a software package called CCD-Autopilot5. The telescope was pointed to the right coordinates, a focus star was acquired, focusing was done, and a guide star was selected without any intervention on my side. Fourty-seven images were acquired in the course of four nights during the first week of September.

Image processing was done in PixInsight. Because there is a weather station connected to the software, the only thing I still have to modify is to add a motor to the observatory roof, so it can be opened and closed electrically. When all that is finished, totally unattended observations will be possible from my back garden.

More information, and a full-size version of this image may be found at: http://www.astrobin.com/55502/

Copyright: Albert van Duin
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