Note. The size of the full Moon is marked, as a gray circle, for a scale.

(The apparent size of the full Moon is about 30', that's 0,5 degrees)



Natural color composition from the emission of ionized elements, R=80%Hydrogen+20%Sulfur, G=100%Oxygen and B=85%Oxygen+15%Hydrogen to compensate otherwise missing H-beta emission. Star colors are mixed from the NB channels, Red=H-a, G=O-III and B= 85%O-III + 15%H-a.This composition is very close to a visual spectrum.



Image is shot with a QHY8, Tokina AT-X 300mm f2.8 lens and Baader narrowband filter set, H-a, S-II & O-III

Original versions from November 2008, with technical details:

http://astroanarchy.blogspot.com/2008/11/sh2-157.html



Sharpless object 157 locates at middle of the image field, it looks like a giant termite head to me. At Ten a clock position are two objects, closer to the center lays the "Bubble Nebula" and little bit further an open cluster M52. The bright emission nebula, just left from the upper center, is NGC 7538. There are several open clusters in the image area, including NGC 7510, King 19, Mrk 50.

Distance from Earth is about 8100 light years and the central emission area, Sh2-157, has an angular dimension about 60x60 arc minutes. (Full Moon is about 30 arc minutes wide.) The shape of the nebula is coursed by a stellar wind, a radiation pressure, from several massive young stars.