Location / Date

Zellerndorf, Sept 2013

Telescope / Mount / Guiding

ASA 10" Astrograph, ASA 2" Barlow Corrector 1.8x (focal length: 1620mm)
ASA DDM60, no Guiding

Camera / Exposure

Canon EOS 500Da
2 panel mosaic, total 79 x 15min ISO 400 (~ 20h)

Processing

Theli, Fitswork, PixInsight, Photoshop

Notes

NGC 7331 is a spiral galaxy about 50 million light-years away in the constellation Pegasus. It was discovered by William Herschel in 1784. The background galaxies are about one tenth the apparent size of NGC 7331 and so lie roughly ten times further away. Their close alignment on the sky with NGC 7331 occurs just by chance. This group of galaxies is also called the Deer Lick Group.

The five visually adjacent galaxies of Stephan's Quintet are NGC 7317–7320. Four of the five galaxies form a physical association, Hickson Compact Group 92, and are involved in a cosmic dance that most likely will end with the galaxies merging. NGC 7320, however, is a foreground object roughly 40 million llight-years away, significantly closer than the others at about 290 million ly, and not part of the Hickson association.
A sixth galaxy, NGC 7320C, probably belongs to the association: it has a redshift similar to the Hickson galaxies, and a tidal tail appears to connect it with NGC 7319.

Published in the ASA Calendar 2015