Thor’s Helmet is an emission nebula with an ionized HII region in the constellation Canis Major. The name of this nebula stems from it striking resemblance to the helmet of the famed Norse God of thunder and lightning.
Thor’s Helmet is composed of cosmic dust and gas, which is revealed to have blue-green appearance through astrophotography. NGC 2359 spans roughly 30 light-years across, and appears as an interstellar bubble that has been inflated by a central Wolf-Rayet star.
NGC 2359 – Thor’s Helmet
NGC 2359 – Thor’s Helmet Nebula captured from my backyard.
Thor’s Helmet lies about 15,000 light years away from Earth. Through astrophotography, we can take a closer look at Thor’s Helmet by collecting long exposure images that uncover the bright emission gases in visible light.
The photo shown below was captured from my backyard using a color camera and Celestron 8″ RASA F/2 telescope. You can click on the photo to see a larger version of the image.
To find Thor’s Helmet, point your telescope about 8 degrees north east of the brightest star in the sky, Sirius. Through the eyepiece of a modest telescope (8″ Dobsonian), this nebula will appear as a fuzzy glowing patch of gas, and may even reveal some of the arcs extending from the central region.
Thor’s Helmet Details
- Common Name: Thor’s Helmet
- Designations: NGC 2359, Sharpless 2-298
- Constellation: Canis Major
- Size: 30 light-years
- Apparent Magnitude: 11.45
- Distance: 15,000 light years
The photo shown above was created by stacking several long exposure images together to enhance the quality of the signal (light) and reduce noise. Each exposure was 60-seconds in length, which eventually became over 2 hours of total exposure time after integration. (138 x 1-minute exposures = 2 hours, 18 minutes)
A 1-minute exposure of a deep sky target is relatively short in the world of astrophotography. However, this was more than enough time to pull out the intense details of Thor’s Helmet thanks to the fast F/2 focal ratio of the imaging telescope.
The telescope used for my photo (Celestron 8″ RASA F/2).
There are several factors that have contributed to my successful image of NGC 2359. The basic principals of deep sky astrophotography include accurate polar alignment, precise focus, and collecting enough images to create a healthy signal-to-noise ratio.
The composition of this nebula lends itself well to narrowband imaging, particularly using Ha and OIII filters. To capture the image on this page, I used a duo-narrowband filter that blocks almost all of the artificial light present in my Bortle Class 8 backyard, yet lets the delicate light from the emission gases through.
The ZWO ASI294MC Pro Color Astronomy Camera.
The camera used for my image was a ZWO ASI294MC Pro. This is a one-shot-color dedicated astronomy camera, that can be cooled to reduce the amount of noise collected in each image. The camera was controlled using the ZWO ASIair wifi device that allows me to automate a sequence of images using my tablet.
I ran my image of Thor’s Helmet through the free image annotation service from Astrometry.net. I highly recommend uploading your astrophotography images to this website to see exactly which deep sky objects you have captured in your image.
Thor’s Helmet (NGC 2359) and the surrounding cataloged deep sky objects.
As you can see in this wide field annotated image, there are not a lot of surrounding deep sky objects in the immediate area of NGC 2359. However, you can see that the Thor’s Helmet is divided into a few parts (NGC 2359 and NGC 2361), and includes a nearby open star cluster (NGC 2374).
It is also interesting to see the label for IC 468, as I can not tell what separates this region from outer nebulae of Thor’s Helmet overall.
From the northern hemisphere, one of the best times to photograph this target is in late winter. From my latitude at 43 degrees north in Ontario, Canada, Thor’s Helmet reaches an altitude of about 33 degrees in the southern sky by late February.
The star map below shows the location of the Thor’s Helmet Nebula and its proximity to the star Sirius.
The location of the Thor’s Helmet Nebula in the constellation Canis Major.
Video (European Southern Observatory)
The following video gives you an incredible view at the Thor’s Helmet Nebula by the European Southern Observatory (ESO).