Explanation: Very faint but also very large on planet Earth’s sky, a giant Squid Nebula cataloged as Ou4, and Sh2-129 also known as the Flying Bat Nebula, are both caught in this scene toward the royal constellation Cepheus. Composed with a total of 20 hours of broadband and narrowband data, the telescopic field of view is almost 4 degrees or 8 Full Moons across. Discovered in 2011 by French astro-imager Nicolas Outters, the Squid Nebula’s alluring bipolar shape is distinguished here by the telltale blue-green emission from doubly ionized oxygen atoms. Though apparently completely surrounded by the reddish hydrogen emission region Sh2-129, the true distance and nature of the Squid Nebula have been difficult to determine. Still, a recent investigation suggests Ou4 really does lie within Sh2-129 some 2,300 light-years away. Consistent with that scenario, Ou4 would represent a spectacular outflow driven by HR8119, a triple system of hot, massive stars seen near the center of the nebula. If so, the truly giant Squid Nebula would physically be nearly 50 light-years across.Credit: APOD, NASA.

In natural light (crominance rgb), there are few traces of the extensive facilities hydrogen nebula. Almost invisible bilobate structure emitting in the band of twice ionized oxigen.

This image shows instead as taking in the band of ionized hydrogen (HII) begins to appear the structure of the whole nebular sh2-129

In this last image obtained in the band twice ionized oxygen disappears completely structures ionized hydrogen, but it should be noted that bilobate and truly fascinating generated from the issue of OIII.