Yesterday, I was watching the hundreds of crows that circle near my house at sunset. This is a daily ritual before they fly off to their nocturnal roost that is about 10 miles (16km) away as the crows fly.

Had these birds been humans, I suspect that you might recognize (be able to distinguish) individual members of this large group. However, being crows, they probably all look the same to you; you've probably never had the need to 'discriminate' among different members of the population. As humans we are pretty good at ignoring differences and lumping things together into large, impersonal collections. We do it with everything: crows, trees, flowers...stars... However, once we decide that differences are important, we are quick to classify, stereotype, then judge, etc.

We all probably know there are different classes of stars, types of galaxies and varieties of nebulae, but because we may not 'care', we don't bother to learn how to distinguish the individual entities. This, to me, is sad--it means that we have chosen to neglect the uniqueness of phenomena.

Today I take a closer look at SH2-252, inspired by @Gary Imm's  fine image, to better appreciate its uniqueness. S252 is 'located' in the constellation Orion, but is part of the Gemini OB 1 Stellar Association, which I discussed briefly in my last image, here. This general area has a number of other designations, including NGC 2175, NGC 2174, IC 2159, or as the "Monkey Head" Nebula. These names are somewhat problematic; there is disagreement over the taxonomy. I won't discuss the particulars of that in this description. 

The nebula itself is ionized primarily by a class O6V blue giant, HD 42088, located centrally. In addition, there are at least five other class B stars in the immediate vicinity, surrounded by 'tiny' early ionizing nebulosity, all of which are part of the Gem OB 1 Association. These are best seen on the annotated version and are labelled A, B, C, E, F, after their full designations (e.g., Sh2-252 E). Sh2-252 B is also a radio source (Westerhout 13) and is deeply embedded in its knot of nebulosity. It is not clear if there are other ionizing stars hidden with B, but it is likely so. 

Sh2-252 E is, perhaps, the most interesting of the 5 Type B stars. There are clearly a few companion stars, which is one reason the structure is sometimes referred to as a cluster. More importantly for the imager, however, is the barely visible semicircular/ovaloid ionization front near the group of stars. This is the type of feature that would be easy to 'erase' in post-processing, yet represents an important part of the developing story of the overall structure. (NB: This structure is quite visible in Gary's image as a slight oval to the left of the central star.)

What strikes me most about this is the marked contrast between the effects of the Type O star compared to the five Type B stars. Those Type O stars are truly remarkable in their power to affect change over a large area!

To conclude the description of S252, to the 'left' of HD 42088 is the "hard edge" boundary of the nebula. Here are dense clouds of (probably cold) neutral atomic hydrogen and probably carbon monoxide. From our Earthly perspective within this area there are undoubtedly other young stellar objects and pre-main sequence stars resisting the ionization of HD 42088.

Finally, on the annotated version, I've indicated the star Types of 62 Ori, 64 Ori and 68 Ori. They are all Type B stars. If you're interested in a further investigation, find out if these three actually are members of the Gem OB1 Association!

As far as the image quality itself goes, I am happy with the outcome. The off-center placement of the nebula, by the way, was intentional. I was particularly pleased that the  important subtleties of the structure were largely preserved with my RedCat and not eliminated in acquisition or processing. Still, the stars are not my best; atmospheric conditions were difficult on both nights and the l-eXtreme filter affected star color more than usual. HD 42088 was particularly affected--its beautiful blue color washed out from slight overexposure.   

Initially I did not want to image this nebula. I was put off by its relative isolation in the void surrounding Gem OB1 and its lackluster (to me) shape. Too, I was guilty of prejudging it based on a rather silly common name. Although it may not be the best subject for the RedCat, I was clearly wrong about the interesting and unique features of the nebula! It is a good reminder: every star, every galaxy, every nebula, every person, every crow is a unique entity with its own story. Perhaps next time we look we can take the time to truly see what lies in front of us, rather than pass judgment.