This dusty region of Sagittarius is known as the Stingray Nebula or sometimes the Eagle Ray Nebula. Unfortunately, there isn’t any reference data I can find about it.

These dusty regions are full of small particles of silicon, carbon and also contain molecular hydrogen (unlike emission nebula which are made of atomic hydrogen).

This is 24h 10m of LRGB data. For all the technical details, see astrobin.