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Contains:  Extremely wide field
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Galaxies and Dust – The Magellanic Clouds in a Dusty Field, 





    
        

            Gabriel R. Santos...
Galaxies and Dust – The Magellanic Clouds in a Dusty Field

Galaxies and Dust – The Magellanic Clouds in a Dusty Field

Technical card

Resolution: 3600x2700

Dates:Aug. 12, 2018Sept. 8, 2018

Frames:
120x60" ISO1600
23x120" ISO800

Integration: 2.8 hours

Darks: ~20

Flats: ~17

Bias: ~40

Avg. Moon age: 14.69 days

Avg. Moon phase: 2.03%

Bortle Dark-Sky Scale: 3.00

Mean SQM: 21.50

Mean FWHM: 2.85

Temperature: 0.55

Astrometry.net job: 2294815

RA center: 49.768 degrees

DEC center: -74.230 degrees

Pixel scale: 32.105 arcsec/pixel

Orientation: 36.557 degrees

Field radius: 20.066 degrees

Data source: Traveller

Description

This huge rarely-imaged field – almost 40 degrees (or 80 full moons) across – features not only the Magellanic Clouds – which I’ve also imaged recently – but also some fine, incredibly faint nebulosity around the field: Galactic Cirrus.

The Magellanic Clouds are satellite galaxies of our Milky Way. They are naked-eye irregular galaxies, member of the Local Group, located about 160000 and 200000 light years away. Known by locals since Ancient times, the galaxies entered western knowledge with Portuguese explorer Ferdinand Magellan. In his circumnavigation in the 16th century, he identified two fuzzy cloud-like objects easily visible to southern hemisphere skygazers are known as the Clouds of Magellan. [1]

Galactic Cirrus are veils that surround our own galaxy – made of dust and gas in the interstellar space. [3] 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. [3] This dust however is not only strongly present at the North Celestial Pole, but also near the South. The Southern region is however much less frequently imaged. The Cirrus has incredibly faint surface brightness, at ~26-28 mag/arcsec^2, thus it is not easy to capture.

The Magellanic system is an interacting pair of galaxies, and some of the faint dust in the field can help tracking down its past interactions – a research field with lots of unanswered questions. Some of its cirrus features have been detected by Vaucouleurs and Freeman in 1972. [6] A paper by Delgado et al. is a great study that incorporated astrophotographic imaging with camera lenses in the study of the tidal interactions of the pair. It has also been a resource for this write-up, and I recommend reading it at [6].

I find it notable that there are records of visual observations of this nebulosity (!), from Herschel in 1700s, and even today by Mel Bartels. I strongly recommend reading his write-up about IFN, galactic cirrus and its visual observation at [5]
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The galaxies are obvious from dark skies, and look a lot like clouds indeed. The view is also beautiful in binoculars or telescopes. I find it enchanting - almost life changing - that we can see, with our very eyes, the light from such large and distant galaxies - many light years away, many light years across, with myriads of distant stars each... it really puts things in perspective! This wide field is rarely imaged to such depth. I only know a dozen other amateur astroimages of this region on the web. I strongly recommend checking the inspiring images I know about, by Yuri Beletsky [6]; Tommy Nawratil, Hisayoshi Kato and Stefan Buda.

In this image I was very happy to have captured the faint dust of Galactic Cirrus in the field. The exposures were captured in August (23x120”) and in September (120x60”). Especially considering the quite modest optics used – an extremely wide field portrait 40mm camera lens. Dark skies helped a lot, but I did suffer from Light Pollution gradients, as the galaxies do not rise that much. Especially in the lower right corner, SNR and fidelity suffered a bit. I am nonetheless pleased with the result – that I believe to be at the limit of my equipment and conditions: an uncooled color DSLR and rural skies.

Date and Time: August 12 and September 08, 2018; ~4 AM [local UTC-3 time]
Location: MG, Brazil. Rural Skies (Bortle 3-4, SQM ~21.5*calculated)
Camera: Canon EOS 80D (unmodded), at ISO 800 (2’ lights) and 1600 (1’ lights)
Lens: Canon 40mm f/2.8 STM, operated at f/3.5
Mount: Sky-Watcher HEQ5, tracking, guided; and EQ3-2, RA tracking, unguided
Guiding: Starguider 50mm Guidescope + ASI120mm + PHD2; ~1.4”
Exposure Detail: 10x120s + 120x60s. Total 166min or 2.75h

Check the Monochrome, inverted and overstretched revision. It greatly highlights the cirrus.

[1] NASA APOD; Wikipedia; messier.seds.org; [2] APOD 2016/07/25; [3] R. Jay. GaBany cosmotography.com/images/galactic_cirrus.html [4] Alan Sandage, from bbastrodesigns. [5] Mel Bartels, “Herschel’s Ghosts” at bbastrodesigns.com/Herschels%20Ghosts.html ; [6] “Low Surface Brightness Imaging of the Magellanic System […];” Delgado et al. 2016 [at arxiv.org/abs/1602.04222]

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grsotnas
Gabriel R. Santos...
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  • Final
    Galaxies and Dust – The Magellanic Clouds in a Dusty Field, 





    
        

            Gabriel R. Santos...
    Original
  • Galaxies and Dust – The Magellanic Clouds in a Dusty Field, 





    
        

            Gabriel R. Santos...
    B

B

Monochrome, Inverted and Overstreched

Sky plot

Sky plot

Histogram

Galaxies and Dust – The Magellanic Clouds in a Dusty Field, 





    
        

            Gabriel R. Santos...