Horsehead Nebula

Barnard 33

Dark Nebula in Orion

Apparent size:6′ x 4′ arc min
Diameter:2.8 light years.
Distance:1,600 light years.

The Horsehead Nebula is one of the most celebrated astronomical objects: an iconic dark nebula of gas and dust, serendipitously set against the red background glow of the impressive and extensive bright emission nebula IC 434.

This 140 minutes exposure is the second time I’ve imaged it. The first one was marred by a solitary satellite trail, so I wanted to get a clear image this time. Unfortunately my new image has four satellite trails – three are obvious and another is faintly visible when the image is enlarged.

Without the bright star Sigma Orionis, (top left) neither the dark or bright nebulae would be visible. It is a multiple star system which has five component stars. The brightest of them, Sigma Orionis A, is a hot type OB star, nearly six times the radius of the Sun with 18 solar masses. The powerful ultra-violet light from this star is responsible for exciting the ionised hydrogen of the IC434 nebulosity and making it visible for us to enjoy.

Lower right is the bright emission and reflection nebula NGC 2023, which is about 4 light years in diameter. Near it’s centre is an 8th magnitude star.

With covid still active, all my images are still being taken from my suburban front driveway.

Image Data

Feature image date:2021-01-11
Exposure:140 minutes (50.5 sec sub frames x 167)
Field of View:1.54° x 1.02° (up is 151 degrees E of N)

Image Analysis From

Here’s where the Horsehead is located in the sky, using images generated for me by

All Sky

It’s location in the Orion constellation:

Orion Constellation

An annotated image of the object generated for me by

If the Astrometry images do not appear it is because the Astrometry website is sometimes off line.

Telescope Details

SkyWatcher Esprit 120 mm apochromatic 3-element refractor; 840 mm f/l @ f/7.
Field flattener; no filter.
SkyWatcher EQ6-R Pro mount; ZWO ASI120 guide camera.
Imaging camera: ZWO ASI 071 MC Pro (CMOS 28.4mm 16 Mpx).
Software: EQMOD, PHD2, SharpCap, Gimp.
Observatory location: 34° South.

Images © Roger Powell

I’m a founder member of Macarthur Astronomical Society


  1. To the human eye, the Horsehead is really hard to see, right? I thought it was very tiny (even for those of us used to highly magnified views of astronomical objects) It looks so sharp in your photo. 140 minutes! Quite an investment in time!

    Liked by 2 people

    1. I once tried visually with an 8″ but of course could not see it. I know others who have failed too but some have. Probably best in 16″+ scopes. I understand a Hydrogen Beta filter can help.

      The reason why it is so hard to see a dark nebula is that you need to be able to see the faint emission nebulosity behind it. IC434 is listed as only mag +7.3 – but it’s spread over about 600 square arc-minutes. So through a small telescope it won’t register with the human eye.

      Liked by 2 people

  2. That is a beautiful image, Roger. Excellent work.

    I finally got a clear evening. First up were Mars and Uranus. Then, out to try to spot M1. No luck. The sky was not dark enough. I scanned around Taurus and Aldebaran before heading for M42. The Trapezium was excellent.

    It was about 23˚ F. My fingers got really cold and my headlamp quit on me. It was time to quit.

    Liked by 2 people

    1. I’m glad you mentioned M1. I did see it visually with my 8″ SCT about a decade ago but for some reason it never reached the top of my imaging target list until last week and I will be posting the result later this week.

      I was outside in short-sleeved shirt and shorts at 20˚C. 🙃

      Liked by 2 people

      1. Sounds like summer weather. 🙂

        I look forward to seeing your image of M1. I was using a 102 mm scope with not the best sky. I will need to try again under ideal conditions.

        Liked by 1 person

    1. Thanks. I didn’t used to mind them much, as most satellites were launched for scientific purposes and my imaging is just a hobby.

      Now rich people are sending up thousands (!) of satellites for profit. As well as ruining optical imaging by professional astronomers, they are also endangering radio astronomy with their communication signals aimed to give blanket coverage on the ground.

      Liked by 1 person

      1. Remarkable imaging, as usual. As for the satellite trails, wouldn’t it be nice if there were a concerted effort to curtail that inevitable pollution of the night sky. Sending up hundreds, if not thousands of communications beacons, just seems to be an unjustified violation of our natural environment. M 😦

        Liked by 1 person

        1. As of now, 955 Starlink satellites are in orbit.

          Wikipedia: “On 15 October 2019, the United States Federal Communications Commission (FCC) submitted filings to the International Telecommunication Union (ITU) on SpaceX’s behalf to arrange spectrum for 30,000 additional Starlink satellites to supplement the 12,000 Starlink satellites already approved by the FCC”



          Liked by 1 person

          1. Thanks for the link, although it is most upsetting. Elan Musk may talk up remedies, but cautionary experimenting (for the potential of severely invasive night pollution) should have been done (and sanctioned) by small sample testing first, preferably under international jurisdiction. Instead thousands of objects were and are being placed in orbit without fully understanding of the impact on astronomical pollution.
            As the wealthiest man on the planet, now – I wonder …what does care? In the vein of global initiatives to better our collective understanding, and proactive policy – think Global Warming, This is a disingenuous example of planetary pollution at the expense of human-kind, for the benefit of …well, one! Reminds me a little of Rupert Murdock and his less than sincere dissemination of salacious and mis-leading “news.” Very popular is his FOX news, and he??? Very wealthy, …at our expense.
            M 😦


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