Thanks guys. I stretched it beyond the norm to bring out the stars in the sack.
These were some comments from an astrophysics acquaintance:
The image shows the Coal Sack as behind layers of intervening stars. In actual reality the CS is on the inner edge of the Carina Arm, just across the way from our Orion Spur. That puts it on the other (far) side of the Carina Arm whose outer edge directly faces us.
I could spot 7 star clusters in Crux and Hogg 18 in the Coal Sack. Hogg18 is actually nearby in our own spiral arm between us and the Carina arm). I really like the textured detail of the dark clouds; there is a preponderance of filamentary structures from the non-stop tussle between magnetic fields and shock turbulence that afflict all spiral arms. For all its impressive bulk to the naked eye, it's actually a very flimsy thing. Only one of its denser cores (the dark one near Hogg 19) will ever form a few stars. The rest is even now being distorted and pummeled by the shear effect of the spiral arm it is embedded in. In time it will shred into wisps that will wander aimlessly until caught up into some far-into-the-future collapsing giant molecular cloud and, with luck, have another go at making stars.
