From the July 2016 issue

Graphite pencils

By | Published: July 4, 2016 | Last updated on May 18, 2023
The author used a 13mm eyepiece for a magnification of 140x to observe the Crescent Nebula (NGC 6888). Transparency was below average, making it difficult to observe nebulosity in the southern portion of the Crescent. For NGC 6888, the author used a #2 blending stump and a 4B graphite pencil. For both sketches, she used white printer paper and observed with a 16-inch f/4.5 reflector and an Oxygen-III filter. She plotted the stars with 8B, 2B, and 2H graphite pencils. She then scanned the sketches and removed the rough star edges in Photoshop. The images are rotated so that north is to the top, west is to the right.
Erika Rix

For simplicity, I tend to use a #2 graphite pencil for most of my deep-sky drawings. After all, a pencil and paper are all that’s really needed to record an observation. Is a minimalist approach the best option, though? An entire set of graphite pencils could be more useful to render star magnitudes and contrast tones, and HB-grade pencils fit the bill. But what do those grades mean?

The letter H in the grading system designates the graphite’s hardness, the B its blackness. The degree of each attribute is represented by a number. For example, in a set containing 8B, 6B, 4B, 2B, HB, 2H, and 4H pencils, an 8B creates the blackest mark, and also has the softest lead. HB (similar to a #2 pencil) is medium-grade. 4H has the hardest lead and produces the lightest mark. I’ll explain their use with two objects in the constellation Cygnus the Swan.

The Crescent Nebula (NGC 6888) lies at the heart of the swan, 2.7° southwest of Gamma (γ) Cygni. Its elongated shell-like shape measures 20′ by 10′ and contains at its center a magnitude 7.4 Wolf-Rayet star. WR 136 (also known as HD 192163), like others of its kind, is shedding material from its surface and then blowing it away with its strong stellar winds, both building and carving out the Crescent’s distinctive shape.

This faint emission nebula responds well to Oxygen-III (OIII) and ultra-high contrast (UHC) filters, but you’ll need a night of good transparency to observe it. Through an 8-inch telescope, the Crescent resembles a shallow arc that cradles WR 136. It begins at an 8th-magnitude star on its northeast tip and reaches north to a 7th-magnitude double before sloping southwest. The western edge thickens through a 12-inch scope, with knots and bright filaments stretching throughout the arc. Look for wisps of nebulosity in its southern region. Through excellent transparency, increased aperture will reveal its faint oval shape.

The author observed NGC 6894 with a 12mm eyepiece for a magnification of 152x. She used a #2 blending stump and 4B and HB graphite pencils. Due to the planetary nebula’s small size, she used a 3/16-inch tortillon for detailed blending.
Erika Rix
I used 8B, 2B, and 2H graphite pencils to render the star magnitudes in my sketch. I created the faint base layer ofthe nebula with the tip of a blending stump that had graphite on it. With light pencil pressure, I added the brighter details with a 4B graphite and then softened them with a clean blending stump.

I nudged my telescope 6° southeast of Eta (η) Cygni to locate the next target, planetary nebula NGC 6894. It has a magnitude of 12.3 and spans 44″ by 39″. A 9th-magnitude star shines 7.5′ to its north.

NGC 6894 appears as a gauzy circular patch through an 8-inch telescope. The ring surrounding it pops into view with the use of an OIII filter. Increasing aperture to 12 inches reveals a slight northeast to southwest elongation with a star just inside its northwest rim. Through a 16-inch scope, you can spot bright specks along the northwest and southeast edges.

Once I had drawn the star field and base layer of the planetary, I switched to a 4B pencil to enhance the ring. I softened it with a clean blending stump, then added the star on its northwest rim. I rendered the bright specks along the ring with an HB pencil and then softened them by gently tapping with a 3/16-inch tortillon, a blending tool with a firm, narrow tip that works best for tight areas.

It doesn’t take long to appreciate the contrast range provided by a set of HB-grade pencils. Be sure to give them a whirl during your lunar and planetary sessions as well.