IC 2118 - The Witch Head Nebula with Rigel's glow

Updated: Jun 22

Featured on NASA's Sky Facebook Page - February 9, 2020


Capturing the Witch Head Nebula has always been on my astrophotography bucket list. We've already imaged it a couple of times wide field, as mentioned below, but we never had the time to only concentrate on the witch. I drove 4 hours to a Bortle 2 zone in the desert of Arizona, the road was incredibly rough (you might have seen my story on Instagram if you follow us!) and I did not think my car would keep all its tires by the time I got to the site.


I was very excited to start imaging IC 2118, and even decided to take a risk with the framing to make the final result more unique.

You will see the result below, and you might either love it or hate it, but you can't argue that it isn't unique!


Sadly, it only took a couple of hours before clouds decided to roll in, forcing me to pack and drive 4 hours back to Vegas. I can't even describe how relieved I was to reach home with my car still running fine. I truly expected it to explode at any time.

Thanks Toyota for making indestructible cars.


On the right, you can see the setup used to capture the images in this post.




IC 2118 is a very large nebula located 800 light-years away in the constellation Eridanus. A DSLR camera and lens or a wide telescope is required to capture the entire object in the frame. You will also need to spend as much time as you can on it as it is very faint with a magnitude of 13.



The Witch Head nebula got its name because it looks like the profile of a witch. It is facing towards the bright blue supergiant star, Rigel.


Expect to spend several hours on the Witch or you will only be able to get parts of it. We advise capturing it with a DSLR camera lens (left) before attempting it with a telescope. Because of the faintness of the nebula, it is extremely hard to properly center in the camera without using computer software. The gases will not be revealed on your images until they are stacked.


We previously imaged the Witch Head Nebula with a DSLR camera and a 50mm lens.

We spent a total of 7 hours on it at this focal length and you can see the result on the left.


Note that this is a crop from the full image, which you can see on our Barnard's Loop post. You may also want to watch Episode 8 of Galactic Hunter to see us photograph this wide-field target using our DSLR camera attached to our motorized mount.




If you are a beginner astrophotographer, it is a great idea to first attempt this object wide field with a DSLR camera and lens as framing this large object in the field of view of a telescope may reveal to be very challenging. Being so faint, it is also very difficult to use test shots to visualize and properly center the target. With a DSLR camera and mid-focal length lens (50 or 85mm), all you need to do is aim at the very bright star Rigel. This way, you can ensure to also have the Witch Head Nebula in the frame.



Rigel, the 7th brightest star in the sky

Let's quickly talk about Rigel, a beautiful blue supergiant that is also the 7th brightest star in the sky.


I have always loved wide field images of the Witch Head Nebula because it always looks like the witch is staring at Rigel. Although I used a wide telescope to capture this object, there was no way for me to include both the witch and Rigel in the same frame.


I decided to take a risk, and position the bright star just on the outer edge of the frame, and, although the star itself is not visible, its powerful glow is.


You can see what I men below. Sure, this is not going to be for everyone's taste, but my goal was to give this image a "unique" look that was not done in the past. We accidentally learned about the glow bright stars could cause when just outside of the frame when photographing the cluster Messier 103.


Do you love it? Do you hate it? Let us know in the comments below!


IC 2118 in LRGB with the ASI 1600MM


GEAR USED:

Camera: ZWO ASI 1600mm Pro Mono

Telescope: Meade 70mm APO Astrograph

Mount: Atlas EQ-G motorized Mount

Guiding: ZWO ASI 290MM Mini

Acquisition: ZWO ASIAIR

Power: Pegasus Astro Pocket Powerbox

Processing: Pixinsight

ACQUISITION DETAILS:

Total Exposure Time: 2 hour and 30 minutes

Exposure Time per frame: 3 minutes

Filters: L (1 hour) / R (30 min) / G (30 min) / B (30 min)

Gain: 139



How to find the Witch Head Nebula?

The Witch Head Nebula can be found 2.6 degrees east of Rigel, the 7th brightest star in the night sky. Although Rigel is part of Orion, IC 2118 is considered to be in the neighbor constellation of Eridanus.


The Witch Head nebula is extremely faint and almost impossible to see. It is of course not visible with the naked eye, and it is debatable whether it can be spotted with binoculars or not. Using a pair of wide binoculars under truly dark skies might reveal what seems to be an elongated patch of darkness. We personally never managed to see it with ours.


Viewing this nebula with a telescope is also a challenge. The recommended way to do it is to use a small telescope with wide band and narrow filters attached, even then, the Witch Head is far from being impressive visually.



Cool Facts
  • Discovered with Astrophotography in 1909

  • About 900 light-years away from Earth

  • Orion’s brightest star Rigel shines on the Witch’s gases


Processing of IC 2118

The Witch Head Nebula is definitely not a great target for narrowband imaging, so we opted for the 4 LRGB filters:


  1. Luminance

  2. Red

  3. Green

  4. Blue


How much data can you get with each filter?


Below are the combined results for each channel.


From left to right:

  • One hour on L

  • 30 minutes on R

  • 30 minutes on G

  • 30 minutes on B


You may notice that the glow from Rigel is only visible on the Luminance and Red channels. This is because the ASIAir decided to do an automatic Meridian Flip ,midway through the imaging session and did not recenter exactly as it was before...

This also made the reflection on our final image white with a tiny hint of red, instead of being colorful.



Discussing how I captured the Witch


Below is a video explaining how I captured IC 2118. I talk about why I drove so far away from home, show you some videos from the rough road and show a nice time-lapse of the telescope hard at work under the sky.



Final Thoughts

Although I am overall happy with the image. I was expecting to have a full clear night and therefore 7 to 8 hours of data on the witch instead of 2 and a half. I hope to be able to recapture this object next year, without clouds coming out of nowhere.


Have you captured the Witch Head Nebula? Attach your image in the comments and let us know what you used!


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Clear Skies,

Galactic Hunter





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