Sky & Telescope - October 2020 - 29

O MEG A CEN: A K IR A FUJII; NGC 6752: ESO

W The finest globular
cluster, in my opinion,
is 47 Tucanae. A
dense cluster, 47 Tuc
has a prominent core
that may harbor an
intermediate-mass
black hole (a class in
between stellar-mass
and supermassive
black holes), with estimates ranging from
around 1,400 to 3,700
solar masses. While
in Australia, I enjoyed
47 Tuc with big Dobsonians almost every
observing night (even
if only briefly) because
it's a circumpolar object from that location.
Leading Australian
amateur Andrew
Murrell lent me his
20-inch Dob, and with
it at 159× I'd place
47 Tuc just outside
the field and watch
globular-rise: The rich
halo of uncountable
stellar pinpoints would
drift into view, the
concentration of suns
becoming ever greater
until the magnificent
yellow core appeared.
Most observers see
color in its dense
core. Tony Buckley,
my generous host
on several Australian
observing runs, has a
14.5-inch Dobsonian,
and with it at 322× I
could easily resolve
the blazing core all
the way across. A
dark north-south lane
appeared on the inner core's preceding
edge, and an orange
star lay just beyond
the core's westnorthwestern edge.
At 136× numerous
star chains appear in
the halo. With a 30inch Dob at the 2016
OzSky Star Safari in
Coonabarabran, New
South Wales, I could
perceive many additional fainter stars.
All images are
oriented so that north
is up.

Omega Centauri

S Omega Centauri is brighter and larger than
47 Tuc, but since it's looser it isn't quite as overwhelming. It is, however, the Milky Way's most massive globular cluster. As with 47 Tuc, Omega Cen may
host an intermediate-mass black hole in its core. This
globular might even be the remnant of a dwarf spheroidal galaxy whose outer stars have been stripped by
the Milky Way. The fact that a stellar designation was
bestowed upon Omega Cen is curious - with the
unaided eye, large and fuzzy Omega doesn't remotely
resemble a star! After seeing it with Buckley's 14.5-

inch at 136× I wrote in my logbook:

"Mesmerizing! It takes 1.6 fields to show all
of the outliers. There are literally thousands of
resolved stars - quite uncountable. The cluster
is markedly oblate east-west. There are two
adjacent dusky areas in the core arranged northsouth where there are no resolved stars."
In Coonabarabran the 30-inch Dob resolved stars all
the way across these two darker areas.

X NGC 6752 in Pavo ranks third in my estimation, and with its conglomeration of 11th-magnitude sparks, is obvious with the naked eye. Sailing on a cruise to Australia, I was observing from
latitude 46°S while rounding New Zealand's South
Island, and the Pavo Globular joined my short list
of those I've seen with my unaided eye.

Murrell's 20-inch at 159×: "A very large,
sparse outer halo, almost separated from
the inner halo by a gap on the following
side. The inner halo is crossed by seven long
curving star chains, resembling mountain
ridges which converge to a tiny central peak.
The bright innermost core is surrounded by
an outer core composed of faint stars. A red
star is on the northeastern edge of the tiny
innermost core. One degree southeast I saw
the very tight group of four 12th-magnitude
galaxies: NGCs 6769, 6770, 6771, and
IC 4842. This observation of NGC 6752 was
bittersweet because I knew that I could never
again enjoy a first view of one of the sky's
splendors - the Pavo Globular was my last!"
sk yandtelescope.org * OCTOBER 2 02 0

29


http://www.skyandtelescope.org

Sky & Telescope - October 2020

Table of Contents for the Digital Edition of Sky & Telescope - October 2020

Contents
Sky & Telescope - October 2020 - Cover1
Sky & Telescope - October 2020 - Cover2
Sky & Telescope - October 2020 - 1
Sky & Telescope - October 2020 - Contents
Sky & Telescope - October 2020 - 3
Sky & Telescope - October 2020 - 4
Sky & Telescope - October 2020 - 5
Sky & Telescope - October 2020 - 6
Sky & Telescope - October 2020 - 7
Sky & Telescope - October 2020 - 8
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