From the August 2016 issue

Capturing galaxies

By | Published: August 8, 2016

For me, the allure of galaxy observing is teasing details out of the view. These stellar conglomerations come in a variety of shapes, ranging from featureless smudges to spirals or slivers of light with bulging centers. To capture galaxies’ unique forms through sketching, it helps to become adept at using a blending stump.

Blending stumps are tightly rolled sticks of paper with pointed tips at both ends. Although they’re primarily used for blending pencil markings, you can also draw with them. Simply rub the tip of the blending stump through a scrap patch of graphite, and then use it like you would a pencil. Use a photographic classification diagram for galaxies for practice before attempting this technique at the eyepiece.

NGC 7814 provides a good example of how to sketch using blending stumps. For both sketches, the author used a 16-inch reflector on a Dobsonian mount and a 21mm eyepiece for a magnification of 87x. She sketched on white printer paper with graphite pencils and No. 2 blending stumps. She scanned the sketches, then inverted them in Photoshop and softened the stars by adjusting the radius and threshold pixels within the “Dust & Scratches” setting. Both images are oriented so that north is up and west is to the right.
Erika Rix
The constellation Pegasus soars high in the sky this month and provides several galaxies to choose from. One of my targets was NGC 7814, an 11th-magnitude, edge-on spiral galaxy with an extensive central bulge. It lies 2.5° west-northwest of Algenib (Gamma [γ] Pegasi). Spanning 5.5′ by 2.3′, NGC 7814 is nicknamed “Little Sombrero” for its resemblance to the more-famous M104, the Sombrero Galaxy. But unlike its namesake, this galaxy’s narrow dust lane is difficult to see without a large telescope under dark, pristine skies.

Through an 8-inch instrument, the Little Sombrero appears bright and elongated northwest to southeast with a 7th-magnitude star that lies 12′ west-northwest of its center. You’ll also see a pair of 9th-magnitude stars separated by 3′ southwest of the galaxy. (I note these in my accompanying sketch.) The core becomes more condensed within the galaxy’s halo through a 12-inch scope and is nearly stellar using a 16-inch scope.

After plotting the stars in my sketch, I like to add the brightest region of the galaxy first with the blending stump. Then I add layers of graphite gradually to increase its density. As I near the edge, I use nearly all the graphite from the tip of my blending stump so that the halo’s diffuse outer portions appear to vanish.

The Propeller Galaxy (NGC 7479) also has a wispy appearance well served by sketching using blending stumps.
Erika Rix
The next object, NGC 7479, is a barred spiral galaxy that lies 3° south of the 2nd-magnitude star Markab (Alpha [α] Pegasi). NGC 7479 reaches 4.1′ by 3.1′ across at 11th magnitude and sports a bright, conspicuous central bar. Observers have pegged it as the Propeller Galaxy because of its asymmetrical, S-shaped arms that spin counterclockwise and a radio jet that spins in the opposite direction.

NGC 7479 appears through an 8-inch telescope as a north-south, elongated halo with a brightened center. An 11th-magnitude star shines 3′ to its south-southwest. With a 12-inch scope, the ends of the bar begin to curve with hints of spiral arms. Bumping the aperture to 16 inches reveals a nearly stellar center. The faint arm flowing from the southern end of the bar curves westward to wrap around a 14th-magnitude star. Slight wisps of the northern extension will curve off to the east with averted vision.

After rendering the galaxy’s bright central region, I used the excess graphite on my blending stump to extend the bar into the flowing S-shaped arms. My last touch was to add the halo’s soft glow.

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