Deep in the South constellation Apus lies a truly spectacular field of nebulosity. Not far from the South Celestial Pole (at declination -80º), this nebula is very rarely captured, especially in full colour. This image shows a region catalogued by Steve Mandel and Michael Wilson in early 2000s as the 9th and last entry to their "Catalogue of Unexplored Nebulae" [1]. This pioneering project identified the interstellar clouds in optical light, before only known to professional astronomers through infrared surveys. Mandel named the nebulae Integrated Flux Nebula, or IFN, a name that is frequently quoted in amateur astrophotography, but seldomly used in professional astronomy, where "galactic cirrus" is preferred.

The Galactic Cirri are veils that surround our 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. 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. [2] It has incredibly low surface brightness, at ~22-28 mag/arcsec² (fainter than the darkest sky background on Earth), thus it is not easy to capture! 

About MW9, this cloud, Mandel wrote simply: "Spectacular field with dust and galaxies." [1]. There is little available information about it, and only a handful of images online. Full colour images are even rarer*. It has also been referred to as "Jacob's Ladder" by Harel Boren or "Sarah's Nebula" by Michael Sidonio. To me the most interesting part of the field are the background galaxies IC 4633 and IC 4635 that can be seen shining through the dust.

This image represents a real technical challenge and captures to me one of the most spectacular regions of the night sky. Accurately capturing the extremely faint dust requires dark skies, perfect calibration, and very careful processing. The image was captured using my usual modest setup (full frame DSLR and 150mm newtonian), in 2021, in what was at the time the longest single-field integration I had captured (almost 15h). The proximity to the south celestial pole poses an additional challenge, since the target never rises much above the horizon (only ~10 degrees above the local horizon obstructed by nearby mountains and trees). Colour calibration was performed using SPCC. I am quite intrigued by the sublte variation in the hues of brown and gray, from yellowish to greenish. Previous wide field images I captured from the same field (1, 2) do not show as much detail or colour variation. I cannot discard the possibility of imperfect calibration or remaining gradients, but since there are so few deep full-colour images, I can also not say that is the result of a real subtle variation in interstellar extinction. To me, all that adds to the sense of mistery and wonder that the field evokes. Overall, I consider this among my very best telescope images!

It has been a long time since I last published one image here - actually, almost 6 full months! A lot has happened in the past months, and the dedication to other activities meant I could not keep up publishing astrophotography as much as I would like to. But there are many great news with all of you, my friends. As outlined in previous yearly reviews (1, 2), despite not being very active here, I am far from stopping astroimaging! I would like to share what I have been up to in the past years in detail, and I am already preparing new images to post these stories - for now, I can say that I want to go in-depth on how I built my observatory (where a print of this very image hangs in its wall), and how I had the dream-come-true adventure of photographing with friends under some of the best skies on Earth. Stay tuned, I am very happy to be back, and looking forward to sharing many great images and stories with you!

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

• Dates: 19, 20, 21 May, 14, 17 June 2021.
• Location: My Observatory, MG, Brazil. Rural Skies (Bortle 3, calculated SQM ~21.4)
• Camera: Canon EOS 6D (mod) at ISO 1600
• Optics: Custom-built 150/750mm ATM Newtonian Telescope (optics by Sandro Coletti) + TS-Optics MaxField 2" Coma Corrector
• Mount: Sky-Watcher HEQ5, tracking, guiding.
• Exposure Detail: 218x240s. Total integration 872min or 14.5h.
• Software: NINA, PHD2, EQMOD (acquisition); APP, PI, PS (processing).

[1] S. Mandel. The Unexplored Nebulae Project. At: http://www.galaxyimages.com/UNP1.html [accessed though the Internet Archive]
[2] R. Jay. GaBany. Galactic Cirrus. At: cosmotography.com/images/galactic_cirrus.html
*I also recommend checking the images by Brian Boyle, Tel Lekatsas, Jason Jennings, Harel Boren and Michael Sidonio.