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Contains:  NGC 2359, NGC 2360, IC 468, NGC 2353, NGC 2345, NGC 2335, IC 2177, M 50, NGC 2323, The star Muliphen (γCMa)
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Seagull and Thor's Helmet Widefield, 


            Gabriel R. Santos...
Seagull and Thor's Helmet Widefield

Seagull and Thor's Helmet Widefield

Technical card

Resolution: 3600x2400

Dates:Jan. 6, 2019Jan. 8, 2019

Frames: 30x120" ISO800

Integration: 1.0 hours

Darks: ~25

Flats: ~16

Bias: ~50

Avg. Moon age: 1.29 days

Avg. Moon phase: 2.74%

Bortle Dark-Sky Scale: 3.50

Mean SQM: 21.50

Temperature: 16.00 job: 2484118

RA center: 107.428 degrees

DEC center: -11.090 degrees

Pixel scale: 9.849 arcsec/pixel

Orientation: 90.565 degrees

Field radius: 5.919 degrees

Data source: Traveller


This wide field (some 20 full moons across) depicts part of the Constellations Monoceros and Canis Major. The most prominent nebula in the field is the Seagull Nebula, also catalogued as IC 2177. NGC 2327 is near the head, and IC2177 forms the wings of the seabird. The Seagull's wingspan would correspond to about 250 light-years at the nebula's estimated distance of 3,800 light-years [1].

The Seagull Nebula was discovered by pioneering astrophotograher Isaac Roberts. In the article "Nebulae which are not recorded in the Catalogues" [2], Roberts writes: "Nebula in Monoceros in which the star 7.3 mag. BD -10.1848 is involved together with several other faint stars. The nebula is irregularly round, bright, with a wide nebulous band across it [...] The nebula is about 13 minutes of arc in diameter." [2] The nebula was discovered photographically, with Robert's 20 inch reflector telescope at Crowborough, UK.

Right below the Seagull, there's another nebula: The Thor's Helmet (or NGC 2359). It is overall bubble-like, with complex filamentary structures, some 30 ly across [3]. This "bubble" was blown as a fast wind sweeps the surrounding molecular cloud, from the Wolf-Rayet star near its centre - a massive, hot, giant star in a pre-supernova stage. The blue color orifinates from the strong Oxygen III emission. [3]

Nowadays long exposure imaging reveals much more than 13' nebula Robert photographed. The Seagull became a popular target for amateur astrophotographers. I captured the nebula in a very wide field - with the Milky Way around it, with dark nebulas in a very dense starfield. The starfield was a challenge in processing - bringing out the faint Ha nebulosity whilst keeping the stars under control is not a trivial task.

This image is also a relatively quick integration, only 1h, given the unstable weather conditions this time of the year. I was very happy Thor's Helmet was somewhat resolved with my tiny 135mm lens - it is such a beautiful target! I was happy since this is my first successful image of this field, and I look forward to reshooting it in deeper integrations, possibly with higher resolution in the future.

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

Date and Time: January 06 and 08, 2019.
Location: MG, Brazil. Rural Skies (Bortle 3-4, SQM ~21.6*calculated)
Camera: Canon EOS T5/1200D (modded), at ISO 800
Lens: Samyang 135mm f/2, operated at f/2.4
Mount: Sky-Watcher HEQ5, tracking, guided
Guiding: Starguider 50mm Guidescope + ASI120mm + PHD2; ~0.9”
Exposure Detail: 30x120s total 60 min

[1] APOD 21/03/2018 [2] "Nebulae which are not recorded in the Catalogues" Isaac Roberts, Astronomische Nachrichten, 1898 [3] APOD 01/11/2017 ; [4]



Gabriel R. Santos...
License: None (All rights reserved)

Sky plot

Sky plot


Seagull and Thor's Helmet Widefield, 


            Gabriel R. Santos...