The Prettiest Nebula You’ll Never See
Posted by Brian Ventrudo
The region around of the star Alnitak in Orion’s Belt is amazingly rich and rewarding… for astrophotographers. There are many faint emission, reflection, and dark nebulae here, but they’re all frustratingly faint for visual observers. The most famous nebula in this active little patch of sky is Barnard 33, a dark cloud of dust in the shape of a horse’s head superimposed on a hot-pink emission nebula. Here’s a lovely image of the Horsehead Nebula and the surrounding stars and nebulosity…
You won’t have any trouble guessing which of the features in the above image is the Horsehead Nebula. This tiny dark nebula, Barnard 33 (or B33) in the center of this image lies in the foreground of the large emission nebula known as IC434. IC434 is powered by the star sigma Orionis, which lies off to the right of the above image. The bright star just to the left of center is Alnitak, the eastern-most star in Orion’s Belt.
Sadly, this spectacle is not easily visible to observers with small telescopes. B33 is small and its background IC434 is quite faint, so a large-aperture telescope (12” or more) is required to see this complex. Dark and clear sky is also essential. Many observers increase their chances of seeing the Horsehead Nebula by using a special H-Beta filter which improves contrast of the complex against the background sky.
While the Horsehead lies beyond visible detection for most observers, there are a few sights within reach of a small telescope here. Sigma Orionis is a splendid multiple star for a small scope. It’s been covered in a previous article. And Alnitak itself is a pleasing double star. It has a magnitude 1.9 primary and a magnitude 3.7 secondary a relatively tight 2.5” to the south-southeast. Power up to 150x or more to split the pair.
Alnitak also powers the massive Flame Nebula (NGC 2024), seen just below and to the left of Alnitak in the above image. In a telescope, the Flame will easily fit into the same field of view as Alnitak. In dark sky, the nebula lies within reach of a 6” telescope for observers with patience and a good UHC or OIII filter.