68 ASTRONOMY • SEPTEMBER 2015ASTROSKETCHING
BY ERIKA RIXSketch
Minkowski’s
nebulae
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 dis-
covered 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 parallel-
ogram of the constellation Lyra
is a beautiful 13th-magnitude
planetary nebula, M1–64 (PK
64+15.1). At only 17" in diam-
eter, 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 tele-
scope, it appears as a soft gray
disk of uniform brightness. Its
shell becomes detectable using
a 12-inch scope, and whenincreasing the aperture to 16
inches, the nebula brightens to
form a ring. Although the cen-
tral 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 ⅛" (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 con-
stellation 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 mag-
nification of a 16-inch scope
reveals its distinctive footprint
appearance, though depend-
ing 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 [email protected].
Clear skies!For the observation of tiny nebula Minkowski’s Footprint (M1–92), the author used a
16-inch f/4.5 Newtonian reflector with an 8mm Plössl eyepiece and a 2.5x Barlow, for a
magnification of 563x.The author sketched M1–64 here as seen through a 16-inch f/4.5 Newtonian reflector
with a 8mm Plössl eyepiece and Oxygen-III filter, for a magnification of 225x. She
sketched both targets using a Gelly Roll 08 white gel pen, a white watercolor pencil,
white charcoal, a No. 1 blending stump, and black Strathmore Artagain paper. She used
a gel pen to draw 3½-inch diameter sketch circles onto the paper. She removed the
rough edges of the stars and added star glow in Adobe Photoshop. Sketches are
rotated so that north is at the top, west is to the right. ALL SKETCHES BY ERIKA RIXM1-92