Contains:  Extremely wide field
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My Imaging Site: A Remarkable Night under the Milky Way and Airglow, Gabriel R. Santos (grsotnas)

My Imaging Site: A Remarkable Night under the Milky Way and Airglow

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My Imaging Site: A Remarkable Night under the Milky Way and Airglow, Gabriel R. Santos (grsotnas)

My Imaging Site: A Remarkable Night under the Milky Way and Airglow

Equipment

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Acquisition details

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Description

This image shows a beautiful nightscape panorama of my imaging site in a clear night. Much more interesting than my imaging equipment in the lower corner, the night sky is the main display. The July skies in Brazil feature the central region of the Milky Way passing right overhead, and in 2019 it was visited by Saturn and Jupiter. Besides, some interesting colorful lights are to be seen. At first sight they may look like thin clouds. But what exactly are they?

That is one phenomenon of the dark skies: airglow. Its first emission line was identified in 1868 by Anders Ångström, but it took until the 1920s to understand that airglow differs from aurorae, and from the 50s onwards it has been extensively studied by scientists and astronomers [1]. It is caused by solar ultraviolet radiation, that leads to complex chemical reactions and collisions of atoms in the atmosphere, causing them to emit radiation by chemiluminescence. [1] It can appear green or red, with the reddish airglow being formed at altitudes between 150 and 350 kilometres, and mostly formed of Oxygen-based molecules [1].

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This image was acquired in a trip to my dark sky, during the July 2019 holidays. Those were probably the most beautiful nights I have experienced there yet. A few days after rain, the atmosphere was crystal clear, with great transparency and seeing. The very faint airglow was easily captured in wide angle exposures, and, along the DSO images, I acquired some great panoramas and nightscapes as well. This is one of the results: the Airglow was easily visible in the back-of-camera LCD image, and could even be identified at the naked-eye threshold [colourless], sharing the skies with the overhead Milky Way central bulge.

Besides, those were the most challenging conditions as well – temperatures plummeted with the dry and cold air mass, and from 11 pm. it was already below freezing. The lowest temperature, at 6:30 am, was -4.6ºC! Frost (“geada” in Portuguese) covered the early morning landscape: a beautiful sight (the OTA was completely covered in frost!). Indeed, this image was captured in the most amazing imaging nights I’ve ever experienced: pristine, photometric conditions all night; the equipment worked flawlessly, and I imaged/observed the faint airglow for the first time! A great night under our beautiful night sky.

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

Date and Time: 6 July 2020, ~23:00 (UTC-3)

Location: MG, Brazil. Rural Skies (Bortle 3-4, calculated SQM ~21.6)

Camera: Canon EOS 80D (not-modified), at ISO 6400

Optics: Canon EF-S 10-18mm f/4.5-5.6, operated at 10mm f/4.5

Mount: Sky-Watcher EQ3-2, tracking

Exposure Detail: 4-frame panorama; 4x140s; Total 9 minutes

[1] L. L. Christensen, S. Noll, P. Horálek. Light Phenomena over the ESO Observatories I: Airglow. The Messenger 163, European Southern Observatory, March 2016

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My Imaging Site: A Remarkable Night under the Milky Way and Airglow, Gabriel R. Santos (grsotnas)