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The Horsehead Nebula

Dark Nebula w/nebulosity

aka B33, LDN 1630


Minimum requirements to detect: 8-inch scope under dark skies

Everyone wants to see the famous Horsehead in Orion, but few beginners realize just how difficult an object it is.  It is important to consider that this object's fame came about in long exposure photographs which show much more than you can see visually.  To see the Horsehead for the first time you will need to be fully dark adapted, have clear, dark skies, and a large aperture instrument (probably something on the order of a 16").  A narrow band filter such as an H-Beta or UHC filter can really help, and may make it visible in smaller scopes.  Having someone who has seen it coach you can also be a great help.

This is one of those objects that gets easier once you learn to see it.  As usual, knowing what to look for is the key.  Eventually you will be able to find it in smaller instruments or without a filter.

The place to start is the Flame Nebula (NGC 2024) which lies just to the northeast of Alnitak, the easternmost star in Orion's belt.  If you can't see this nebulosity there is no point in looking for the much more difficult Horsehead.  In fact, you need to be able to clearly see the dark lane that crosses this nebula if you are going to have any chance at all.  Spend some time here trying to see as much detail as possible--it's great practice.

You may also want to try and see NGC 2023, the nebulosity surrounding HD 37903.  This 7.8 magnitude star lies to the southeast of Alnitak and is pretty much on the way to the famous Horsehead.  NGC 2023 isn't all that difficult, except that it has a relatively bright star within it.  Some people (myself included) seem to have more difficulty making out nebulosity that surrounds a relatively bright star.  In any case, seeing the NGC 2023 nebula may be a good confidence builder as you move to the main event. Look for a faint, oval haze surrounding the star.

The next stop should be HD 37805, a 7.5 magnitude star that lies about 8' to the southwest of HD 37903.  The Horsehead nebulosity passes pretty much north-south just to the west of this star.  Look for a faint, elongated skyglow.  This area of the sky should look ever so slightly brighter than the surroundings.  An H-Beta filter can really bring it out.  Don't be afraid to use high magnification to increase the contrast, particularly if you aren't using a filter.  But you also don't want to use so much that the nebula fills most of your field of view.  This can also make it hard to detect against the background.  You may want to place HD 37805 out of the field, if possible.

Make sure that you are comfortable and spend a lot of time looking.  A quick look just won't do--you have to relax and work at it.  You should be sitting down, if possible.  It can help if you can keep both eyes open as you look.  If there are any stray lights in the area, sometimes placing a cloth or towel over your head at the eyepiece can make all the difference.

Once you are confident that you can see the feeble glow of the nebula, look for a notch or hole about 8' due south of HD 37805.  Use averted vision.  If you can convince yourself that you have seen a notch, then you can claim success!  With practice over time, and on one of those rare excellent nights, you may see this notch well enough to make out the familiar Horsehead shape.  As always with difficult objects, the best chance for success is to keep looking over and over again.  You may be surprised how much more you can see if you just keep at it!

This is the view in a 12-inch LX200 at 76x. The red areas are where you should look for faint nebulosity. The field of view (circle) is 51'.  North is down and east is to the right.
The long faint nebula is IC 434, but it is the intrusion of the nearby B33 dark nebula complex that creates the famous silhouette of the horses head.  B33 is actually a much larger complex of obscuring dust, stretching several degrees, most of which is found to the east of the IC 434 region.

Seeing the Horsehead with a filter is a real accomplishment; finding it without one is something to very be proud of!

Millennium Star Atlas Vol I Chart 253
Sky Atlas 2000 Chart 11
Uranometria 2000 Vol II Chart 226
Herald-Bobroff Astroatlas B-14 C-53