Sky & Telescope - October 2022 - 43

a
l
ε
225
γ
M103
δ
CASSIOPEIA
α
129
β
Binocular Highlight by Mathew Wedel
Plunge into Cassiopeia
C
assiopeia, mythological queen of Aethiopia, was
the first constellation I learned, but it's so rich
Deneb
α
N o r t h e r n
C r o s s
M29
1
C Y G N U S
Albireo
that I'm still making new connections as I explore it
further. This month we'll look at two open clusters
that let us " see " the depth of space.
Start with 6th-magnitude NGC 129, which sits
DELPHINUS
QUULEUS
0°
about halfway between the 2nd-magnitude stars
Caph, or Beta (β) Cassiopeiae, and Navi, or Gamma
(γ) Cassiopeiae, and just north of an imaginary line
connecting them. The notes on my original observations,
made with 7×50 binoculars, read, " compact,
many stars, rivals M103 under dark skies. " If conditions
are good, by using 10×50 binos you may be
able to spot a nice, even triangle of 9th-magnitude
stars set off a bit to the south of the cluster's center.
Our second target, NGC 225, glows at 7th magnitude
a little more than 2° northeast of NGC 129. To
me, the stars at the cluster's center look like a cup or
a chalice, with fainter lights glittering within. A pleasingly
symmetrical arc of 9th-magnitude stars sits just
east of the cluster.
Of the two objects, NGC 129 looks bigger and
-20°
WHEN TO
-40°
1h
g So
USE THE MAP
Late Aug Midnight *
Early Sept 11 p.m.*
Late Sept 10 p.m.*
Early Oct 9 p.m.*
Late Oct
Dusk
*Daylight-saving time
brighter, so it's tempting to perceive it as being closer
to us. But, in fact, at 5,300 light-years it lies more than
twice as far away as NGC 225. NGC 129 also looks
almost two times as large in diameter (21′ vs 12′), and
if it's twice as distant, it must actually be four times
the size of NGC 225. Astrophysical measurements
bear this out - NGC 225 has a diameter of about 7.5
light-years, whereas NGC 129 is 32 light-years across.
It's nice when the math works out so neatly.
I hope that learning more about the objects you
observe helps you find connections of your own.
¢ Realistically, MATT WEDEL is never going to fit all
of Cassiopeia in his head, but that doesn't stop him
from trying.
sk yand tele scope .o r g * OCTOBER 2022 43
5
M27
Altair
β
η
A Q U I L A
γ
α
°
VULPECULA
SAGITTA
SAGITTARIUS
w
b
M16
i
e
i
n
v
o
c
β
r
u
δ
γ
ε
χ
γ
α
β
Moon
Oct 2
18h
uth
70
β
κ
R
Vega
M92
π
η
H E R C U L E S
ζ
δ
β
ε
M13
S E R P E N S
( C A P U T )
W
e
15h
η
M7 M6
ing
M25
σ
ζ
τ
M22
M8
M21
M20
M17
M23
ε
α
IC4665
M10
M12
O P H I U C H U S
ε
S ERP ENS
( CAUDA )
M11
S C U T U M
12h
B O Ö T E S
Arcturus
L i t t l e
D i p p e r
U R S A
M I N O R
η
Mizar
& Alcor
B i g
D i p p e r
M81
M82
M51
Thuban
β
M57
L Y R A
cin
g
CORONA
BOREALIS
CANES
VENATICI
α
W
N
β
β
δ
U R S A
M A J O R
γ
ε
β
ν
D R A C O
ζ
γ
α
α
aF
+60°
+80°
ζ
ε
γ
9h
gnic
caF
gni
ε
α
β
α
F
a
s
t
θ
Fac
S
W
δ
ζ
γ
µ
α
γ
β
α
ε
η
α
δ
γ
β
α
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