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NGC 7099
Ben 128
Messier 30, ESO531-SC021, GCL-122
RA 21:40:23
Dec -23°11.4'
Globular
cluster 
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This globular cluster is Capricorn was
discovered by Messier in August 1764. His small Gregorian reflector with an
equivalent modern aperture of 2-inches could not resolve it into stars, showing
him only a round nebula without stars: "nebula ... seen with difficulty in
an ordinary telescope of 3.5 feet .. it is round and I saw no star there, having
observed it with a good Gregorian telescope of 104x."
In the Philosophical Transactions, 1814,
William Herschel described it as "a brilliant cluster, the stars of which
are gradually more compressed in the middle. It is insulated, that is, none of
the stars in the neighbourhood are likely to be connected with it. Its diameter
is from 2' 40 to 3' 30 arcseconds. Its figure is irregularly round. The stars
about the centre are so much compressed as to appear to run together. Towards
the north, are two rows of bright stars 4 or 5 in a line. In this accumulation
of stars, we plainly see the exertion of a central clustering power, which may
reside in a central mass, or, what is more probable, in the compound energy of
the stars about the centre. The lines of the bright stars, although by a
drawing made at the time of observations, one of them seems to pass though the
cluster, are probably not connected with it." In the Philosophical
Transactions, 1818, William Herschel wrote: "1794, 7 feet finder, it is but
just visible. 1794, 7 feet telescope. it seems to be resolvable, but is too
faint to bear a high power. 1810, 10 feet telescope. with 71 power, it appears
like a pretty large cometic nebula, very gradually much brighter in the middle.
1783, it appears like a pretty large cometic nebula, very gradually much
brighter in the middle. 1783, with 250 power it is resolved into very small
stars. 1783, small 20 feet Newtonian, 12 inch diameter, power 200, it consists
of very small stars; with two rows of stars 4 or 5 in a line. 1783, large 29
feet Newtonian, power 120, by a drawing of the cluster, the rows of stars
probably do not belong to the cluster. 1784, 1785, 1786, 20 feet telescope,
power 157. A brilliant cluster. 1810, large 10 feet telescope, with 171 and 220
the diameter is 3' 5 seconds; it is not round."
h: "globular, B, lE, bM, 4' long, 3'
broad; all resolved into stars 16m, besides a few 12m. Two lines of rather
larger stars run out N.f."
In the 5th edition of Webb's Celestial Objects
for Common Telescopes it is described as "moderately bright; beautifully
contrasted with an 8th mag star beside it; comet-like with 64x; with higher
powers resolvable. Smythe: 'What an immensity of space is indicated! Can such
an arrangement be intended, as a bungling spouter of the hour insists, for a
mere appendage to the speck of a world on which we dwell, to soften the darkness
of its petty midnight? This is impeaching the intelligence of Infinite Wisdom
and Power, in adapting such grand means to so disproportionate an end. No
imagination can fill up the picture, of which the visual organs afford the dim
outline; and he who confidently probes the Eternal Design cannot be many removes
from lunacy.' E. of Rosse, spiral arrangement of branches. It lies closely
preceding a little north from 41 Cap, a 5th mag star."
Hartung notes that it "lies in a fine
contrasting field. The well-resolved centre is compressed and two short
straight rays of stars emerge N.p. while from the north edge irregular streams
of stars come out almost spirally. With outliers the cluster is nearly 4'
across. Resolution is just apparent with a 3-inch and clear with a 4-inch."
The catalogued size is 11', but Walter Scott
Houston found the stars concentrated into a core about 2' across, "which is
surrounded by a halo perhaps twice as large." It is about 8th magnitude
and a bit over 10' in diameter. Its bright centre and easily resolved edges
make it an interesting object for small telescopes. The cluster makes a long
isoceles triangle to the southeast with 34 & 36 Capricorni.
William P. Clarke (San Diego, California, USA)
writes in the The Webb Society Nebulae and Clusters Section Report No. 10, July
1992: "Large, bright and well-resolved. Irregular outline with 3 chains of
stars extending NW, N and NE. (21-inch f/20, x140)."
Tom Lorenzin: “8M; 6' diameter; small and
soft-edged with much brighter middle and 12M stellar core; little larger and
brighter than N7006; not quite round with brighter stars concentrated in NW
quadrant; 10M star 8' to W; two stellar strings extend 1' from core-one radial
due N; the other, tangent to outer edge, heads N and a little W; bright star
20' E and a little S is 5.5M 41 CAP.”
Donald J. Ware:”The only object of note
in this constellation, this globular cluster is about 8-10' in diameter, and is
fairly well concentrated to the center.”
Steve Coe, using a 13” f/5.6, notes: “M30
Bright, large, much brighter in the middle. I counted 45 stars at 220X. This
nice globular is easy in the 11X80 finder. It is elongated 2x1 E-W and there are
several nice chains of stars on the south side. There are many faint stars that
form a backround glow. Sentinel 13" 7/10--easy in 11X80, 100X--bright,
pretty large, resolved, elongated 2X1 in PA 90, bright middle. 330X--22 stars
resolved, much brighter middle, several chains of stars curve out from core,
mostly on north side.”
11x80: “A pretty small,
bright, round glow. Has a small star to the west-southwest of the cluster; this
appears brighter than it is shown on the Uranometria chart; more 8th than 9th.”
(exurban skies) [AS]
8-inch Meade, 18mm eyepiece, 36’
fov: “Pretty large, irregular bright globular with a well
compressed core gradually becomes brighter. Pinpoint startrails in the fringes,
and a nice asterim circle of faint stars to the north and a star to the west.
About 9 arc minutes in size.” [MS] |
