Sketch Minkowski’s nebulae
Erika Rix guides readers through sketching the challenges of small nebulae.
By
Erika Rix |
Published: Monday, July 27, 2015
If you caught my previous column, you may have tried your hand at using the white-on-black sketching technique for deep-sky objects. Now it’s time to step it up a notch. The challenge isn’t always in the complexity of the object, but rather its size.
In 1946, a German-American astronomer named Rudolph Minkowski (1895–1976) released a new list of 103 nebulae. He discovered these by examining objective-prism survey plates obtained by William C. Miller with a 10-inch refractor at Mount Wilson Observatory. With several interesting small nebulae to choose from, I’ll share two of my favorites.
Tucked within the parallelogram of the constellation Lyra is a beautiful 13th-magnitude planetary nebula, M1–64 (PK 64+15.1). At only 17" in diameter, it’s often overshadowed by the more obvious Ring Nebula (M57). You can locate M1–64 nearly halfway between the Ring and Zeta (ζ) Lyrae.
Through an 8-inch telescope, it appears as a soft gray disk of uniform brightness. Its shell becomes detectable using a 12-inch scope, and when increasing the aperture to 16 inches, the nebula brightens to form a ring. Although the central star isn’t visible, you should be able to spot a faint star at its north rim. This object responds well to Oxygen-III and ultra-high contrast filters.
Smaller objects require precision sketching tools. Use a 1/8" (No. 1) blending stump to apply a thin, round layer of white pastel within the star field to render the planetary’s disk. If you observe the shell, add its gentle glow softly with a white pencil.
Smaller yet is Minkowski’s Footprint (M1–92), a bipolar reflection nebula in the constellation Cygnus. Due to its diminutive 4.5" by 11.5" size, I used the magnitude 5.4 star 9 Cygni as a home base and then star hopped 20' north-northeast until I recognized the ladle-like star pattern in which the nebula resides. A magnitude 9.7 star lies another 1' farther north.
Looking through an 8-inch telescope, M1–92 is stellar, but it softens at 200x. You’ll notice an elongation using a 12-inch scope so that it resembles a close double. Pushing the magnification of a 16-inch scope reveals its distinctive footprint appearance, though depending on sky conditions, you may not see a separation. The northwest lobe is brighter and nearly two-thirds the size of its tapered southeast component.
I drew the large circular lobe with a white pencil and then blended with a No. 1 stump. I needed only slight dabs to soften its edges while leaving the center bright. I used the residue that remained on the stump’s tip to smudge in the heel.
Be sure to check out my next column for a demonstration on sketching solar prominences, and as always, feel free to share comments or questions with me at erikarix1@gmail.com. Clear skies!