Object: Constellation: Coordinates: Size: Brightness:
NGC 772 Ari 01h59m / +1900' 7.2' x 4.3' 10.3mag

The unbarred spiral galaxy NGC 772 (Arp 78) in the constellation Aries on October 26 / 27, 2019 and on January 20, 2020. The galaxy is around 200'000 light years in diameter and is surrounded by several satellite galaxies - including the dwarf elliptical, NGC 770 - whose tidal forces on the larger galaxy have likely caused the emergence of a single elongated outer spiral arm that is much more developed than the other arms. Halton Arp includes NGC 772 in his Atlas of Peculiar Galaxies as Arp 78, where it is described as a "Spiral galaxy with a small high- surface brightness companion". NGC 772 is about 130 million light years from Earth and was discovered by Frederick William Herschel in 1785 (source: Wikipedia).

Fourty-six 3 minute exposures at ISO 800 were added for this shot with the DeepSkyStacker software (resulting in a 2 hour and 18 minutes exposure) and the final image processing was done in Photoshop. Unfortunately, half of the fourty-six frames were blurry due to an impressive temperature drop of 35 C (45 F) within two hours. The mirror just couldn't cope with this.
Equipment: Canon EOS 450D Baader modified camera, TeleVue Paracorr Type II coma corrector, 16" f/4.5 "Ninja" dobsonian telescope riding on a dual-axis Tom Osypowski equatorial platform, Lacerta MGEN autoguider, Lacerta off axis system (field of view comparison: image of the moon with the same equipment).

Search chart for NGC 772. Map © 2020 "The Mag-7 Star Atlas Project", www.siaris.net. Map is slightly modified. The map can be downloaded here .