I'm not sure how this nebula got its name, but I'm sure someone had a good reason for it. This nebula shows why you should never mix hydrogen and dust in your own galaxy. They just don't mix well. The horse's head is an arm of dust probably thrown off by the star in the lower left corner. I know. It doesn't look like a star, but think about how a car's headlights look coming out of heavy fog. Looks kind of similar, huh. The dust you are seeing is sort of like the black pencil lead stuff left over when you sharpen your pencil.
Which filter helps you if you're an astronomer studying the red hydrogen gas? Which filter would help if you're an astronomer trying to study the stars right on the boundary between the hydrogen gas (upper half) and the dusty area (lower half).
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Horsehead
Nebula
