The Caldwell Objects

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ulae in de Cheseaux's list, he could not have
scrutinized Omega Centauri because it was
always below his horizon. Clearly, then, his
description was based solely on Halley's impressions.
Omega Centauri's true nature also eluded
the keen eye of Louis de Lacaille, who listed the
object in his 1755 catalog under the category of
"nebulae without stars." Mind you, Lacaille
observed with a simple ½-inch 8x telescope — an
instrument inferior to most of today's binoculars.
He described it as a "[nebula] in Centaurus; with
simple view, it looks like a star of 3rd magnitude
viewed through light mist, and through the
telescope like a big comet badly bounded."
Some sources imply that Sir John Herschel
first identified Omega Centauri as a star cluster.
His famous account makes the notion plausible:
"The noble globular cluster ω Centauri, beyond
all comparison the richest and largest object of its
kind in the heavens. The stars are literally
innumerable, and as their total light when
received by the naked eye affects it hardly more
than a star of the 5th or [5th to 4th] magnitude,
the minuteness of
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each may be imagined: it must however be recollected
that as the total area over which the stars
are diffused is very [considerable] (not less than a
quarter of a square degree), the resultant
impression on the sensorium is doubtless thereby
much enfeebled, and that the same quantity of
light concentrated on a single point of the retina
would very probably exceed in effect a star of the
3rd magnitude."
But alas, even this claim is wrong. Who,
then, first resolved Omega Centauri into stars?
None other than James Dunlop, that "gentleman
astronomer" from Parramatta, New South Wales.
It is the 440th object in his 1827 catalog. Omega
Centauri, wrote Dunlop, "is a beautiful large
bright round nebula, about 10' or 12' diameter,
easily resolvable to the very centre; it is a
beautiful globe of stars very gradually and
moderately compressed to the centre; the stars
are rather scattered preceding and following
[west and east], and the greatest concentration is
rather north of the centre: the stars are of slightly
mixed magnitudes, of a white colour. This is the
largest bright nebula in the southern
hemisphere."
Deep-Sky Companions: The Caldwell Objects