Messier 13 is the most famous deep sky object in Hercules. It’s one of the most spectacular globular clusters in the sky so it tends to overshadow everything else in the constellation. It turns out there are some other pretty spectacular sights lurking there!

Though, to be fair, if you saw this with what used to be a conventional processing workflow, it would look much flatter – a dark patch with maybe a hint of additional dust. These were called dark nebulae because they made dark patches on the photographic plates they used. dark patches were spots where dust blocked the stars behind. Thanks to modern digital sensors, we can “see the darkness” now. What gets revealed is not a featureless dark blob but a dusty mess that reveals the beauty in a dusty galaxy.

While this went down in Lynds’ catalog as LDN 648 (the top left of the big dark path and LDN 650 (the very small dark spot to the right of the large one, Lynds never catalogued the larger dark spot between. And, as images like this make clear, this is all one big dust cloud. It might be that the larger, lighter colored cloud is dust that was blown of the darker, denser area. It looks like that to me but that’s just speculation.

One thing to note is that these dusty clouds redden the stars that do shine through. This is exactly the same effect that happens at sunrise and sunset where the dust in our atmosphere scatters the blue light and lets the red pass through.

I haven’t found any reference data on how far away it is so I can’t report on any interesting details about it.

This is 35h of LRGB data. You can find all the technical details at astrobin.