Kneaded erasers

When comparing the versatility of erasers, the kneaded variety wins my vote every time. Among its attributes, two stand out above the rest — pliability and tackiness. It has the consistency of putty so that you can mold it to tackle even the smallest areas. And due to its absorbing nature, you can lift lightly applied graphite from the sketch without damaging the paper. This combination lets you perform the gradual fading and precise erasures that are key to creating detailed drawings. Let’s talk about small areas first.

There’s a striking 12th-magnitude planetary nebula, NGC 2022, nestled near the head of Orion the Hunter. You will be able to spot it at 100 power through small- to medium-sized instruments as a grayish 25" disk on an imaginary line from Lambda (λ) Orionis to Betelgeuse (Alpha [α] Orionis). Bumping the magnification to 275x reveals a defined ring structure with a hazy center. Larger scopes show a south-southwest to north-northeast elongation with brightened western and eastern edges. Simply for fun, see if you can spot a kite-like asterism flying just northeast of the disk.

While making my sketch, I found it necessary to remove excess graphite from within the ring in order to represent the gauzy center — remember that when using graphite on white paper for deep-sky objects, you’re creating a negative sketch where starlight appears dark on a light background. After kneading the eraser to soften it, I molded it into a pointed tip. Then, with light pressure, I dabbed the tip inside the ring until I’d lifted sufficient graphite from that area to match the eyepiece view. Simply fold the eraser into itself to refresh it as needed.

Next, I’ll use M79 in Lepus to demonstrate a technique called subtractive drawing. I captured the distinct shape of this winter globular cluster by removing graphite from the paper with a kneaded eraser, as opposed to adding it with a blending stump.

Nearly 4° south of Nihal (Beta [β] Leporis), this fuzzy 8.7'-wide cluster shines at magnitude 7.7 with a dense core, appearing comet-like through small telescopes. You may even resolve a few stars near its halo. Train a medium- to large-sized instrument on M79, though, and you can expect to pick out over 40 stars, along with a strand running along its eastern edge and another reaching 4' south.

Globular clusters rarely have an even shape when you observe them closely. I created a patch of dense graphite for the core of the cluster and used a blending stump to spread it outward for the halo. Once I added the stars, I molded the eraser to form a thin tip and then gently rubbed away the graphite to draw the cluster’s distinct shape. Because I had plotted the stars with hard pencil pressure, the process left these smaller points intact.

When it comes to kneaded erasers’ value for astronomical sketching, the two examples I’ve provided only scratch the surface. I’ll leave it to you to explore it further during your own nights under the stars.