LDN 673 is one of many dark nebula in the Milky Way. It it caused by dust blocking the light creating these abstract dark patterns through the dense star fields.
This one is in the constellation Aquila and is relatively small. Our field is only 0.9 degrees in the horizontal and a bit less in the vertical. The boundaries of these are somewhat arbitrary and this field doesn’t cover the full extent of the nebula.
This is 18.5 hours of LRGB data. Processing and other technical details at astrobin.