Long time, no see! It has been a while since I posted a finished work in AstroBin. Life and everyday activities prevented me from publishing images here (a process which includes searching and writing a detailed description for the targets). But the passion for astrophotography remains as strong as ever, and I have lots of images (probably around 50, some in various stages of processing, a few already post-processed) and exciting news to share with you (including new gear, and big news regarding my personal observatory). I hope I can post them in next weeks - stay tuned :-) In the meantime, here is an image acquired almost a year ago, post processed early this year, and finished recently.

This beautiful wide field spans some 50 degrees across, in the border between Eridanus and Taurus constellations. In between the myriads of stars of the image, and the faint pervasive dust clouds (in dark brown) an interesting feature can be seen glowing in bright red: a patch of nebulosity known as the Eridanus Loop. It is a huge HII bubble east of Orion and possibly an old SNR. Its brightest part, in the left side of the image was catalogued as Sh2-245. It is suspected to be connected to the much brighter Barnard’s Loop in Orion, forming together the Orion-Eridanus Superbubble.

Amateur images of this object are extremely rare. Part of this is attributed to the immense challenge to record the faint nebulosity, requiring exceptionally dark skies, careful data reduction and post-processing skills. This image is one of the few of colour images of this target, especially using a consumer DSLR camera (modified for enhanced Ha sensitivity, but without dedicated monochrome Ha data). It was assembled as a deep sky mosaic - the final image is composed of 8 panels (2x4 grid), blended and integrated. For more inspirational work on the Barnard’s Loop, refer to Mr. Hirofumi Okubo’s image of the same region; or to the excellent narrowband-grayscale Ha images by Dennis di Cicco and Sean Walker (originally published in April 2009 S&T magazine); or the deep Ha mosaic by John Gleason. Hisayoshi Kato's deep wide field of the region also show the faint loop. Astonishingly, very experienced observers Mel Bartels and Reiner Vogel also report seeing the loop visually with large telescopes under exceptional conditions!

To me, this image marks a technical achievement of being able to capture the faint dust in brown and nebulosity in red, as well as a stunningly intriguing target. I was fascinated by the shading and color variation of the dust - from deep browns to more grayish tones, possibly a result of interstellar extinction. It is one of the handful of color images of this target, and likely its first Brazilian capture. The data was acquired from my dark sky in MG, Brazil, in Nov. 2021, from a photometric night (rare in our rainy spring-summer season). Despite the short integration time, I was surprised with the result. It was certainly one of the most difficult mosaics to process: the image could really use double or four times the integration time - the starfield is remarkably busy, and the nebulosity remarkably faint. It was a balancing act that involved three completely different reprocessings. At the end, I called this version finished, but look forward to incorporating more data later this season.

Finally, I recommend checking out the starless version (Rev. C). I am usually not a fan of starless images as final pictures (despite their value during post-processing), but in this case I think it looks beautiful, almost surreal. The nebulosity is greatly highlighted. What do you think?

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

Date: 4 November 2021
Location: My Observatory, MG, Brazil. Rural Skies (Bortle 3, calculated SQM ~21.3)
Camera: Canon EOS 6D (mod) at ISO 800
Optics: Samyang 135mm f/2, operated at f/2.4
Mount: Sky-Watcher HEQ5, tracking, guided
Exposure Detail: 8-panel mosaic (2x4), each 15-17x120s, total 128x120s = 256min = 4.3h