I actually wanted to write about Sharpless 261, Lower's Nebula, but when scanning Wikisky, I stumbled over this nice group of three Str÷mgren spheres just north of it, which had been a favorite of mine for a long time. So it will be Sharpless 257 and friends today, in the constellation of Orion, between Orion's head and the feet of Gemini.
IC 2162 (= Sh2-257)
RA 06 12 50
Dec +17 58 33
group of four emission nebulae
Sharpless 257 (also IC 2162) forms together with Sharpless 254 and 255 a group of three nice Str÷mgren spheres, which a friend of mine and I dubbed the "Three Snowballs" due to their milky appearence at the eyepiece. The image above is a color composite of the DSS2 images.
This is a DSS red image with the different parts of the group labeled.
And this is a finder chart from my Sharpless Observing Atlas.
My observing notes for this nice group during a night of very good transparency are as follows:
In the 24 mm eyepiece of my 22-Inch Dob, the two more compact nebula 255 and 257 were easily visible with H-Beta filters as milky, well defined areas, each surrounding a star in the middle. Sharpless 254 was somewhat more diffuse, but could be seen without retinal torture. The entire group fit into the field of view of the eyepiece and the contrast between the diffuse 254 and the more compact 255 and 257 was particularly beautiful.
With the UHC Filter, all three were still visible, yet much more difficult than with H-Beta. As to be expected for low-excitation HII regions, they were hardly visible with the OIII filter.
I tested as well the small nebula Sharpless 258, which is to the left on the image and might be some kind of reflection nebula. As there was nothing visible immediately, I did not try to push this, in particular as there are superimposed stars, which might be deceiving. Sh256, on the other hand, the small patch between 257 and 254, was well visible as a separate glow detached from the main mass of Sh257.
So this group is a nice target for the new year. A bit fainter than M42 but nevertheless a nice and interesting object. So...
"GIVE IT A GO AND LET US KNOW"
GOOD LUCK AND GREAT VIEWING!