IC 434

Diffuse nebula
Orion
RA 05 40 40
DEC -02 27 00

Size 90’ x 14’

IC 434 is a faint emission nebula that runs mostly south from Alnitak, the eastern star of Orion’s belt and is seldom, if ever, observed for its own merits because it silhouettes B33, the iconic Horsehead Nebula. The h-beta filter that is often referred to as “the Horsehead filter”, is actually the IC 434 filter because it boosts the contrast of the emission nebula enough to make the Horsehead much more visible. But let’s put the Horsehead aside for now and appreciate its perennial second fiddle, IC 434.

IC 434 DSS from MegaStar.jpg

Located about 1500 light years away, it’s part of the huge Orion Molecular Cloud Complex along with all the other well-known nebulae in Orion. But IC 434 is subtle and needs dark skies to be appreciated, even with the h-beta filter. Under the darkest skies it’s surprisingly easy to see without a filter, and can be detected in telescopes as small as 100mm.

The brightest area runs south from Alnitak and to me looks like a rather broad swath of nebulosity with the eastern edge having a distinct boundary, especially around the Horsehead nebula which is why it’s so well defined. Fainter areas extend west, most prominently just west-southwest of Alnitak.

You can’t ignore several other brighter nebulae in this area, the most intricate being NGC 2024, the Flame Nebula. There’s also a string of MAC galaxies running mostly south from Alnilam to just west of the Horsehead Nebula, but that’s another whole observing project.

All this covers a huge chunk of sky. The 90’ x 14” size listed above is from MegaStar, but any measure of IC 434 is simply a reference because deep photos show it extending half way from Alnitak to M42: (http://apod.nasa.gov/apod/ap131029.html).

I began my sketch this past weekend from my usual Oregon observing location under good conditions – 21.25 SQM and good seeing – with my 28 inch Newtonian and a 20 year old Lumicon h-beta filter using magnification from 135x to 235x. The best views I've ever had have been from Steens Mountain in southeastern Oregon at 7400 feet – from there the brighter striations within IC 434 are visible and, dare I say, bring the Horsehead to life.

IC434sketch_crop.jpg IC434sketch_crop_invert.jpg


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