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What filter did you use to view the horsehead?.This is a object that is on my viewing list and I hope to eventually see this.I've been in the mist of a being a glutton on galaxies,but will be turning my attention back(somewhat,I'm not done with galaxy viewing,the glutton in me beckons!)to nebula viewing. My last session was one of the best I've had in spite of the moon,so I was thinking about the horsehead for some reason lol

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Hi Bert,

The hydrogen beta is, hands-down, the best filter for Horsehead hunting. The trick is to use a filter that enhances IC 434, the background nebula against which the dark nebula, B33 (Horsehead), is seen. IC 434 is a low-excitation nebula with almost no OIII emission. The OIII emission is so minimal that an OIII filter makes IC 434 almost impossible to see. And if you can't detect IC 434, the Horsehead is out of the question.

By contrast, a hydrogen beta filter will enhance IC 434, making it easier to detect. This in turn punches up the contrast between the Horsehead and IC 434. Good transparency is critical to Horsehead hunting. Dark skies are also a must but transparency is the real key. From the high elevation sites I use, I've never failed to see the Horsehead, unfiltered, with my 18 inch. I've seen the Horsehead unfiltered in a 6 inch from a site that isn't quite as dark but enjoys the same excellent transparency.

A UHC filter offers a slight enhancement of IC 434. It's only a modest improvement so, if you can see the Horsehead with a UHC filter in place, it will usually be visible unfiltered, too. And as mentioned above, an OIII filter is deadly; it's a Horsehead killer.

Bill in Flag

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Grand Canyon Adventure
Lowering the Threshold

18" Obsession
4.5" Meade 4500
10x50 Swift Audubon

Cosmic Voyage

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What filter did you use to view the horsehead?.This is a object that is on my viewing list and I hope to eventually see this.I've been in the mist of a being a glutton on galaxies,but will be turning my attention back(somewhat,I'm not done with galaxy viewing,the glutton in me beckons!)to nebula viewing. My last session was one of the best I've had in spite of the moon,so I was thinking about the horsehead for some reason lol

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Well, it is getting a bit low and hard to see now (at least from the Northern Hemisphere), but in general, the H-Beta filter is the one to use. I have seen the faint band of IC 434 and just managed to glimpse the tiny notch of the Horsehead itself under dark skies using only my 100mm f/6 refractor (15x) when the H-Beta filter was in, although the view was somewhat marginal. There have been those at moderate to high altitude sites who have seen the Horsehead in scopes in the four to six inch range *without* using a filter, but this tends to be somewhat less frequent, as it requires excellent conditions and a little effort to get out a lot to try. The object is visible in larger apertures without filtration, but this again requires quite good conditions. It can be seen in my 9.25 inch SCT, but still is more of a vague slightly darker gap in the very faint nebulosity than a detailed figure (at least without a filter). Put in the H-Beta and, while it is still quite dim, the object stands out a lot more with hints of the "snout" using averted vision. The DGM Optics NPB filter has been known to help the Horsehead as well, although perhaps not quite as much as the H-Beta filter does. Clear skies to you.

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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info

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