This wide and deep field reveals a lot of faint dust in the constellation Sagittarius, around the irregular dwarf galaxy NGC 6822. In an apparently black section of our night skies, no striking emission nebulae, and no famous star cluster are to be seen. But long and deep exposure of this seldom imaged area reveals a myriad of stars and tendrils of faint dust. This 10-degree-wide picture reveals not only the DSO pair (Barnard’s Galaxy and nebula Sharpless 63, to its East/left), but also the galactic cirrus.

Galactic Cirri are veils that surround our own galaxy – made of dust and gas in the interstellar space. It was first noticed on optical glass plates recorded at Palomar Observatory and subsequently cataloged by B. T. Lynds, in 1965 [1]. In the 2000s, Steve Mandel noticed faint cirrus in deep, wide field photographs near the North Celestial Pole, and labelled the nebulosity as the IFN, or the Integrated Flux Nebula. [1] This dust however is not only strongly present at the North Celestial Pole, and the term IFN might be used to describe the cirrus in other parts of the sky. In this particular image, the region is filled with this nebulosity, whose details are rarely imaged.

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Upon planning my astrophoto sessions, I came across a possibly nice field of IFN nebulosity around Barnard’s Galaxy. I decided to go for the faint challenge, and in 2018 started to collect photons on the area. In 2019 I continued the pursue, imaging from the dark skies of Goiás (12th EBA). Finally, I integrated the 5+ hours of data, with some added complexity given the different calibration files (different sessions, ISOs, f/ and exposure times).

Post processing was extremely difficult: the area is close to the center of the Milky Way, and the starfield is really dense. Most of the exposures featured some additional unfiltered IR halos (improved in 2019), that, despite being tiny, contributed to an overall increase in star size. This combination of faint dust and stars was very difficult to balance in processing. This also made gradient modelling a great challenge, and at the end I still feel the final-image background could be improved. As there are so few images of this field, processing this image was also somewhat of a discovery to me, and many times I simply did not find something to compare it to. Overall, after many tries, I decided to call this version Final, at least for now. Perhaps with more skill (and data) I will definitely re-image this challenging image.

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

Dates: 8 July 2018, 7 September 2018, 30 July 2019 and 2 August 2019.

Locations: MG and 12th EBA, GO, Brazil. Dark-Rural Skies (Bortle 2.5-3.5, calculated SQM ~21.5)

Camera: Canon EOS T5/1200D (modded), at ISO 400 and ISO 800

Optics: Samyang 135mm f/2 operated at f/2, f/2.4 and f/2.8

Mount: Sky-Watcher HEQ5, tracking, guided

Exposure Detail: 30x120s + 27x240s + 50x180s. Total 318 min or ~5h

[1] R. Jay. GaBany. Galactic Cirrus. cosmotography.com/images/galactic_cirrus.html