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Contains:  Witch Head nebula, IC 2118, The star τOri, The star Rigel (βOri), The star ιLep, The star λEri, The star 68Eri, The star Cursa (βEri), The star 66Eri, The star ψEri, The star 63Eri, The star 62Eri, Part of the constellation Eridanus (Eri)
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Witch Head Nebula, 





    
        

            Gabriel R. Santos...
Witch Head Nebula

Witch Head Nebula

Technical card

Resolution: 3600x2509

Dates:Sept. 9, 2018

Frames: 54x120" ISO800

Integration: 1.8 hours

Darks: ~20

Flats: ~20

Bias: ~50

Avg. Moon age: 29.26 days

Avg. Moon phase: 0.08%

Bortle Dark-Sky Scale: 3.00

Mean SQM: 21.70

Mean FWHM: 2.80

Temperature: 2.00

Astrometry.net job: 2337227

RA center: 77.064 degrees

DEC center: -7.352 degrees

Pixel scale: 9.777 arcsec/pixel

Orientation: 90.496 degrees

Field radius: 5.959 degrees

Data source: Traveller

Description

This is the great Witch Head Nebula, right between Orion and Eridanus constellations. Also known as IC 2118, this interstellar cloud is some 70 light years across, 800 ly away. The nebula reflects Rigel’s starlight, the 2nd brightest Orion star. Dust grains scatters blue light more efficiently than red, the cause of its blue tint. [1] This very wide field presents the nebula in its cosmic context – in a field glowing with faint nebulosity, and the surrounding Barnard’s Loop, NGC 1788 (in the left edge), Sh2-278 (bottom); and LBN 945 (faint dust in the left hand side).

The Witch’s Head has a very interesting story surrounding its discovery. It was discovered photographically by the German astronomer and pioneering astrophotogtapher Max Wolf. [2] Some sources state 1909 as the date. Others, January 16th, 1891. (I believe the latter is the correct one, but I have not yet found Wolf’s original publication.) I found Wolf's original publication. What a wonderful read! Wolf published a 1905's article, but it was hinted in plates from 1891! He wrote "The nebula is composed of several streams of nebulosity, and has the appearance of foggy clouds driven by a fresh breeze" [5] I strongly recommend reading it at [5] However, this nebula was likely observed some 100 years before that! William Herschel listed NGC 1909 in 1786, as a large 2º nebula, in…. an empty area of the sky – but the description matched IC2118’s. It is believed Herschel observed the right nebula but made a mistake when annotating its position on the sky. He annotated it as being 11 minutes of time east of Rigel, when it’s actually west! This being a recent conclusion, the Witch is known as IC 2118 instead of NGC 1909. [2]

The faint outskirts of the Barnard’s Loop are in the background, glowing in red. The field also presents Sh2-278 in the bottom edge. It is rarely photographed, but is a very interesting and beautiful, associated emission and dark nebula (LDN1634). Studies concluded it is either a remnant of Orion Molecular Cloud (formed from Orion OB1) or pushed to its location by the winds and pression of OB association. [3] Finally, in the upper left corner is NGC 1788, a reflection nebula also known as The Cosmic Bat, some 1300 ly away. A fitting name to this spooky area! [4]
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This image was captured in a very cold morning, from my session of 09/09. As described in some of my previous images, Spring and Summer (Oct-Mar) is the rainy period in Southeastern Brazil. Therefore, I have a great “hole” in my images for objects in those RA coordinates. I used the moments before sunrise to capture this image in a almost freezing 1-2ºC ambient temperature! A challenge, but the pristine clear skies were worth the effort! I was really surprised by the quality of the original data – processing was a pleasure and the SNR very good, which made it a surprise to find so much faint dust.

I consider this to be one of my best works to date! The colors and nebulosity makes a charming, eye-catching spectacular field. I publish it a couple of days before the Oct 31st: my Halloween image!

Constructive criticism, comments and suggestions are more than welcome in the comments section – including on the new labelling. Thank you for taking your time to look at this image.

Date and Time: September 09, 2018; ~4h [local UTC-3 time]
Location: MG, Brazil. Rural Skies (Bortle 3-4, SQM ~21.7*calculated)
Camera: Canon EOS T5 (modded), at ISO 800
Lens: Samyang 135mm f/2.0, operated at f/2.4
Mount: Sky-Watcher HEQ5, tracking, guided
Guiding: Starguider 50mm Guidescope + ASI120mm + PHD2; ~1.3”
Exposure Detail: 54x120s. Total 108 minutes

[1] APOD, 2015/10/30; [2] Seligman Celestial Atlas cseligman.com/text/atlas/ngc19.htm#1909 ; [3] Sakib Rasool; hansonastronomy.com/sh2278/ ; galaxymap.org; [4] Wikipedia; APOD 2013/04/19; [5] The Great Nebula of Eridani. By Dr. Max Wolf adsbit.harvard.edu//full/1905MNRAS..65..528W/0000528.000.html

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grsotnas
Gabriel R. Santos...
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Witch Head Nebula, 





    
        

            Gabriel R. Santos...