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Abell 31 in Cancer, April/May 2026
Nikon D7500a, 600mm f/4 + 1.4 TC (840mm f/5.6)
ISO 1600, 72 x 5 min. (6h),
L-Ultimate Optolong Dualband Filter
Abell 31 (also known as Sh2-290 or PK 219+31.1) is an ancient planetary nebula in the constellation of Cancer. It is estimated to be about 2,000 light years away. Our sun will also end like this: the outer shells will be dispelled and a resulting white dwarf will slowly cool down and disappear. Other small bright planetaries look similar to planets in a telescope, that is where their rather misleading name derives.
Abell 31 was discovered in 1955 by the American astronomer George Ogden Abell on the photo plates of the Palomar Observatory Sky Survey (POSS).
Abell 31 is mainly composed of hydrogen and gas. The blue oxygen occupies the central region and makes up the bulk of the nebula, while the red hydrogen makes a ring at the nebula's edge. This object is very old, and consequently, it is very large, dim and therefore has a low surface brightness. It is dispersing into the interstellar medium.
That is why this image was captured over several weeks, when there was no moon and a very dark sky. It was rather frustrating to have many cloudy nights. In total I got 6 hours of 5 min. images, which I combined in PixInsight and post processed in Photoshop and Lightroom.
