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NGC 6752
Bennett 121
Dun 295
RA 19:10:51.8
Dec -59° 58' 55''
Globular
cluster |
James Dunlop observed it from Paramatta, New
South Wales, and included it as No. 295 in his catalogue of 1827. Using a 9-inch
f/12 telescope, he described it as “a pretty large and very bright nebula,
5' or 6' diameter, irregular round fgure, easily resolved into a cluster of
small stars, exceedingly compressed at the centre. The bright part at the centre
is occasioned by a group of stars of some considerable magnitude when compared
with those of the nebula. I am includined to think that this may be two clusters
in the same line; the bright part s a little south of the centre of the large
nebula.” He recorded the cluster on 5 occassions.
h: “globular, B, R, p rich, psmbM, 5',
stars of 2 sizes, 11-12m and 15..16m, S.p. is an elegant first class double
star.” On a second occassion he called it “globular, B, rich, psmbM,
7', the stars are of 2 magnitudes, the larger 11m, run out in lines like crooked
radii. The smaller, 16m, are massed together in and round the middle.” His
third observation was recorded as “Globular, B, L, R, rather irregular,
stars 11..16m, comes up to a blaze in the middle; semidiameter in RA = 25
seconds; fine; one star 7-8m is S.p. out of the cluster.” It was next
recorded as “globular, The central mass consists of smaller stars than the
outside.” The final record reads: “globular, B, irreg R, psvmbM, all
resolved; stars 11..15m; diam 5'; has a star 7m 4' south and 14 arcseconds
preceding.”
Bailey, examining a Bruce plate (Harvard
Annals, Vol 72, No 2), describes it as “very remarkable, very bright,
globular cluster, much compressed, diameter 20'.”
Bennett observed it with a 5-inch short-focus
refractor, including it in his list of cometary objects as number 121. His coded
description describes it as a circular extended object, fully or partially
resolved into stars under a higher magnification of with a larger aperture.
Hartung described it as “moderately
condensed... the central region about 3' wide, and the unusually bright outliers
extending over 15', involving an elegant pair (7.7+9.3, 3”, 238 ) Many of
the brighter stars of the cluster are in curved loops and arms, and look
distinctly reddish.” He notes that even a 3-inch “shows scattered
stars in and around a nebulous haze”.
Peter F. Williams from New South Wales,
Australia, calls it a “striking object when viewed through instruments
ranging from binoculars to large aperture telescopes. The impression of one
globular cluster superposed upon another larger and fainter globular cluster
matches well the view presented though my 6-inch f/8 Newtonian. My observing
notes for 1977 portray a large, bright globular in which resolution is obvious
throughout. Stars within the cluster seem to occupy two distinct levels of
brightness, a number of 9th and 10th mag overlying innumerable stars of
magnitude 12 and fainter. Outlying members stretch the cluster's diameter to
about 10' but the striking feature is a brighter central region 3' across from
which stars seem to radiate in a loose spiral pattern. The ease of resolution
places NGC 6752 in company with five other great southern globulars: NGC 104,
NGC 5139, M4, NGC 6397, and M22. My notes for this object do not, however, make
reference to color apart from stating that all stars appeared white in color.”
Glen Cozens writes than “An 8-inch shows
a half-dozen spidery legs emanating from the cluster's centre and separated by
dark patches.”
ASV Journal Vol 24 No 3 June 1971: “just
visible to naked eye. Excellent in telescopes.”
Marilyn Head writes: “To the right and
just below Ara lies NGC 6752 in Pavo, my very favourite glob. Nicknamed the ‘starfish’,
it is 13,700 l.y. away, has a magnitude of 5.3, a Shapley class of VI and is a
stunning view with the bright stellar ‘arms’, for which it was named,
curving away from the centre. As Hartung describes: ‘a most lovely object’.”
[“10 Easy Globs!” by Marilyn Head (105 Owen Street, Newton,
Wellington, Aotearoa / New Zealand; [email protected])]
The RNGC (Sulentic and Tifft 1973) notes that
this is a 7.0 mag globular cluster. The mean blue magnitude of the 25 brightest
stars, excluding the 5 brightest, is 13.36. Data from Harris: Integrated V
magnitude 5.40 Central surface brightness, V magnitudes per square arcsecond
15.20 Integrated spectral type F4/5 Central concentration, c =
log(r_total/r_core); a 'c' denotes a core-collapsed cluster 2.50c: Core radius
in arcmin .17. [“Catalog Of Parameters For Milky Way Globular Clusters”,
compiled by William E. Harris, McMaster University. (Revised: May 15, 1997; from
http://www.physics.mcmaster.ca/Globular.html; Harris, W.E. 1996, AJ, 112, 1487)
]
11x80: Massively bright
globular, with a brighter star south-west; with averted vision, its light is
spilt out over an area perhaps 13 arcmin in diameter. [AS]
15.5-inch f/9 Newtonian: At
220x, this globular cluster is a spectacular object. It has a very small but
definite nucleus of tightly concentrated stars, and appears elongated
northeast-southwest. To the south and west of the nucleus is a bright star. The
cluster is very well resolved, except for the nucleus, which appears
banana-shaped. There are many obvious star chains which seem to start near the
nucleus and loop outwards. Particularly noteworthy are two chains, a large one
on the southeast and a tiny one to the northeast. Each chain forms a complete
loop, (the smaller one is more clear), enclosing a dark patch on the inside of a
loop, rather like a necklace of pearls. This cluster is best observed slowly,
letting your eye play with the shapes that the stars seem to trace out across
the face of this globular. (suburban skies) [AS] |
