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On the trail of dark nebulae

July 2013: How to sketch dark nebulae that you'll find silhouetted against the Milky Way this summer.

RELATED TOPICS: ASTROSKETCHING | DARK NEBULAE
Erika-Rix
When most amateur astronomers think of dark nebulae, the Horsehead Nebula (Barnard 33) immediately comes to mind. If you haven’t seen it, you’ve surely seen the Great Rift — a region in the constellation Cygnus the Swan that provides stunning naked-eye views of the dark veins running through the Milky Way.

Such clouds of cold interstellar gas and dust, which eventually give birth to stars, present themselves as dark patches silhouetted against the brighter backdrop of stellar light. They can be difficult targets to sketch because of their low contrast. Therefore, a dark sky really helps, as does the use of the current crop of high-quality wide-field eyepieces.
Lynds-Dark-Nebula-7 sketch
Eric Graff sketched Lynds Dark Nebula 7 while observing through a 6-inch f/6 reflector at 60x. He used a #2 pencil and black ink on white card stock, an artist chamois, and blending stumps for blending. He then scanned and inverted the sketch. // Eric Graff
So, this month, to get you started sketching dark nebulae, I suggest you head toward the southern region of the constellation Ophiuchus the Serpent-bearer. There, the Pipe Nebula (Barnard 59, 65–67, and 78) spans a whopping 7°. With your naked eyes, you can see it cradling magnitude 3.3 Theta (θ) Ophiuchi to the northwest. Nestled within the Pipe Nebula, where the stem of the pipe meets the bowl, is a portion of LDN 7, a nebula recorded by Beverly T. Lynds in her classic Catalogue of Dark Nebulae.

This horseshoe-shaped cloud measures 15' across with an opacity of 6. In the case of dark nebulae, astronomers developed an opacity scale that runs from 1 (the lightest) to 6. If you observe LDN 7 through a 6-inch telescope at a magnification of 50x, you’ll notice that the horseshoe opens to the southeast. You also will spot dark, slender wisps radiating north and south from its bend. A dense area of stars lies just outside its western edge. While in the area, try splitting β128, a challenging double star 15' to the west.
Lynds-Dark-Nebula-11 sketch
Lynds Dark Nebula 11 appeared faint through a 6-inch f/6 reflector at 120x. Eric Graff used a #2 pencil and black ink on white card stock, an artist chamois, and blending stumps. He then scanned the image and inverted it. // Eric Graff
Nearly 4° northwest of Theta Oph, you’ll see LDN 11, more commonly known as Barnard 57. It stretches some 5' northeast to southwest and also has an opacity of 6. B57 has a crescent shape when observed through a 6-inch telescope at 50x. Located near the center of the bend is a magnitude 12.6 star, and a 12th-magnitude one lies at its diffuse northwest tip. See if you can spot the “trapezium” of magnitude 11 to 13 stars that lies just 10' to the northeast. Looking south, there’s also a nice strand of 9th- to 11th-magnitude stars meandering east to west.

When you start to sketch a dark nebula, provide its framework by plotting the star field first. Then use a blending stump loaded with graphite to directly shade in unresolved starlight and patches of luminosity. By default, this shading will create the boundaries of the nebula. When using graphite on white paper, remember that you’ll be working in negative format. This means that bright areas are rendered dark and vice versa. Take your time, and soon you’ll be creating high-quality sketches of dark objects to go with those of bright ones.
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