The Caldwell Objects

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NGC 1261
Type: Globular Cluster
Con: Horologium
RA: 03 h 12 m 15.3 s
Dec: -55° 13'01"
Mag: 8.3
Diam: 6.8'
Dist: 55,500 light-years
Disc: James Dunlop, included in
his 1827 catalog
J. H ERSCHEL: Bright; large;
irregularly round; 2.5' diameter;
all resolved into equal stars [of]
14 [th] magnitude.
Has a star [of] 9th magnitude [at a position angle of] 45
[degrees] north following [to the northeast]. 3' distant. (h 2517)
O UR NEXT C ALDWELL OBJECT, NGC 1261, is
an unobtrusive globular cluster inhabiting an
inconspicuous swath of celestial real estate in the
unassuming constellation of Horologium, the
Clock. Aside from its 4th-magnitude lucida,
Alpha (α) Horologii, that constellation is but a
dim sprinkling of 5th- and 6th-magni-tude suns
paralleling the southeastern bank of the celestial
River Eridanus. The Abbe Nicolas Louis de
Lacaille created the constellation during his
famous exploration of the southern skies from the
Cape of Good Hope between 1751 and 1753. But,
as Julius Staal reminds us in The New Patterns in
the Sky, Lacaille named the constellation
Horologium Oscillatorium, the Pendulum Clock.
Lacaille wanted to commemorate the
technological achievement of not the clock but the
pendulum, which was designed to make the clock
run more accurately. Unfortunately, as time
marched on, it became popular to refer to the
constellation as simply Horologium. In doing so
we have denied
The Caldwell Objects
GC/NGC: Globular cluster, bright, large, round, partially
resolved, some stars seen.
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ourselves a vital piece of astronomical history.
The best way to find NGC 1261 is to start at lstmagnitude
Achernar (α Eridani). Some 6° to the
north-northeast are the roughly 4th-magnitude
stars Chi (χ) and Phi (φ) Eridani. Now use your
binoculars and look 3½° southeast of Phi Eridani
for a 2°-long acute triangle comprising 5thmagnitude
Eta (η) and Zeta (ζ) Horologii and a
6th-magnitude star. (Zeta Horologii marks the
southern tip of that triangle.) Next, look a little
more than 2° southeast of Zeta Horologii for a 1°wide
right triangle of magnitude-6.7 stars.
(Finding these triangles should not be a problem
because they contain the brightest stars in their
respective sky regions.) At this point it may be
best to switch to your telescope and put in a
wide-field eyepiece, because NGC 1261 shines
weakly at magnitude 8.3 and its disk is small and
compact. You'll find it just shy of 2° due east of
the 1°-wide triangle. TW Horologii, a semiregular
variable star that fluctuates between magnitudes
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