Sky & Telescope - July 2022 - 55

I began by aiming the refractor at
+22°
orangey Delta Sagittae, one of only two
stars in the constellation I could spot
with my bare eyes. From there it was
a short hop to fainter Zeta less than
¾° northeast. Zeta looks single at low
power, but it's a strongly unbalanced
binary known as Struve (Σ) 2585. Its
primary element is magnitude 5.0,
while the secondary sun, 8.3″ away, is
four magnitudes dimmer. My apochromat
split the pair at 50×, and it was
quite appealing at 100×.
From Zeta Sagittae, I re-aimed the
apo 1° northeastward to a spot just
across the Sagitta-Vulpecula border.
There, at the foot of the Fox, my 8×50
finderscope picked up a 40′-long isosceles
triangle, the baseline of which is
anchored by two 7th-magnitude stars.
The triangle's vertex to the east-northeast
is marked by the superb low-power
double Struve Appendix Catalogue
I 48 (ΣI48). Its 7.1- and 7.3-magnitude
components, 41.7″ apart, make this an
eye-catching " headlights " double. And
those headlights gleamed nicely in my
apo at 28×.
Also on my list was 6.6-magnitude
Theta (θ) Sagittae, which glimmers
1.5° northeast of Eta (the tip of my
arrow). Theta is a triple, also designated
Σ2637AB and Σ2637AC. The 8.9-magnitude
secondary (component B) lies 11.6″
from Theta, while the 7.5-magnitude
tertiary (C) is separated by a breezy
91.9″. The triangular system was glorious
in the apo at 28×.
Main Messier Meal
After the appetizers, I was hungry for
the main course: globular cluster M71.
To be honest, though, M71 isn't a
hearty meal. Viewed in a backyard telescope,
this lower-tier globular is small,
faint, and not very globular-like.
Deep-sky observers - me included -
often comment that the visual appearance
of M71 is somewhere between an
unconcentrated globular and a remote
open cluster. The little guy is only 7.2′
in diameter and glows lamely at magnitude
8.4. Its most prominent members
are magnitude 12.1, and the vast
majority are much dimmer. The lack of
VULPECULA
θ (Σ2637)
ΣI48
η
γ
ζ (Σ2585)
SAGITTA
3
4
5
6
7
8
9
M71
Harvard 20
δ
α
+18°
13
11
10
ε
+16°
20h 10m
20h 00m
19h 50m
19h 40m
LITTLE ARROW Sagitta is tiny and dim but not hard to find in the band of the Milky Way between
much larger neighbors Cygnus and Aquila. Oddly, neither Alpha (α) nor Beta (β) Sagittae is
the constellation's brightest star - that honor goes to 3.5-magnitude Gamma (γ).
luster is a bit odd, given M71's distance
of approximately 13,000 light-years -
not far for a globular (brilliant M13 in
Hercules is almost twice as distant).
Fortunately, M71 enjoys a rich
setting in the glorious summer Milky
Way. Situated halfway between Delta
and Gamma Sagittae, M71 lies 21′
east-northeast of 9 Sagittae, a 6th-magnitude
marker 1.2° east of Delta. The
scene is attractive - a couple of 9thmagnitude
stars shine ¼° east-southeast
of the globular, while a half-dozen
mostly brighter ones (9 Sagittae among
them) are clumped a similar distance
westward. A 10th-magnitude guardian
stands protectively near the northeast
edge of the fragile cluster. Fainter sparks
are everywhere.
That lovely field, spanning about
40′, showed beautifully in the refractor
at 38×. M71 itself was a pale puff
that resembled an uncondensed, tailless
comet adrift in space. Upping the
magnification to 100× turned the comet
into a cluster. M71 exhibited a distinct
graininess bordering on partial resolution,
though with no concentration
toward the center. Increasing to 129×
didn't help, as the cluster's light was
spread too thinly to observe effectively.
My 8-inch Dobsonian working at
50× framed the field perfectly. M71
exhibited individual stars at 75× and
was pleasingly (albeit faintly) resolved
at 175×. The outskirts of the cluster
blended seamlessly into the surroundings.
To my eye, it seemed as though a
portion of the Milky Way had gathered
into a ragged pile of grain. I estimated
its diameter to be maybe 4′. Several
leading lights - possibly foreground
stars - were scattered atop the diminutive
patch. One cluster-width northeastward,
I detected a few more individual
specks of light dotting the area between
the hazy patch and the guardian star. In
the end, the best view was had at 100×.
Some folks might dismiss M71 as a
poor-quality globular. I disagree - I've
seen way worse. My nomination for the
worst glob blob (Messier division) is
M72, in Aquarius. M72 is often a noshow
in my pea-soup of a sky, whereas
the lone Sagitta Messier manages to
punch through the suburban murk.
Give it a try!
Care for a little dessert? An obscure
sk yand tele scope .o r g * JULY 2022 55
β
+20°
9
Star magnitudes

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Sky & Telescope - July 2022

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