In his legendary Photographic Atlas of Selected Regions of Milky Way, E. E. Barnard writes about this nebula: “[...] a large dark area (B312), very sharply defined at its northern edge and at the northwest side. It diffuses to the south and elsewhere. There is a heavy sprinkling of small stars all over it. It is almost elliptical in form, its diameter northwest and southeast being 1°50’ while the shorter diameter is 27’. There is a less definite dark area to the east of it.” [1] 

It is featured in plate number 34 – “In Aquila and Sagittarius”, originally captured from Mount Wilson around 1905, when Barnard worked there, with the objective of photographing the Milky Way as far south as possible. He captured “154 plates [...] with the 10-inch Brashear doublet, and 151 with the 61 -inch Voigtlander doublet, the exposures being simultaneous, almost without exception. The original negatives of 40 of the 50 photographs in this volume were made during this time at Mount Wilson.” [1]
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I always found this nebula fascinating. The shape reminds me of a dark sea stingray, swimming in the myriads of stars of the central Milky Way. This particular image is a small preview of a larger mosaic I am working on, that should include very pretty bright nebulae to the right of B312 (do you know which? – comment below ;-). This is rendered as a crop from a 2-panel mosaic, with a total integration time under 3 hours, as a pure natural-color RGB image taken with a 150mm/6” Newtonian telescope and full-frame DSLR camera, under my dark sky observatory in two nights of June and July 2021. 

There are not too many images online that highlight the nebula in itself. If you liked this image, I suggest you check the amazing work by the APO Team, which includes narrowband data showing the faint H-alpha wisps that surround the region, which are only hinted in this broadband composite. Nevertheless, I am quite pleased as how it turned out, especially the colorful starfield that contrasts with the deep dark nebula. 

Stay tuned for the complete mosaic, and for many more images captured over the last months from my dark site. I had very productive sessions but I have a long processing queue (some 400h of unpublished/unprocessed photons). Hopefully this is the first of a sequence of new images that should follow shortly =D

Constructive criticism, comments and suggestions are more than welcome in the comments section! 

Dates: 18 June and 29 July 2021.
Location: My Observatory, MG, Brazil.
Rural Skies (Bortle 3, calculated SQM ~21.6)
Camera: Canon EOS 6D (mod) at ISO 1600
Optics: 150/750mm ATM Newtonian Telescope (optics by Sandro Coletti) + TS-Optics MaxField 2" Coma Corrector
Mount: Sky-Watcher HEQ5, tracking, guiding
Exposure Detail: cropped from 2-panel mosaic, each 15 and 28x240s. Total integration 43x4min or 2.9h. 

[1] E. E. Barnard. A Photographic Atlas of Selected Regions of the Milky Way, pp. 7-8; pp. 241-245. First published 1927 in two volumes by the Carnegie Institution of Washington. Reedited and republished under the direction of Gerald Orin Dobek, by Cambridge University Press, 2011.