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NGC 6809
Bennett 122
Messier 55, GCL-113
RA 19:39:59
Dec -30°58.0'
Globular
cluster |
This globular was discovered by Lacaille and
included in his 1755 catalogue as Class I No. 14. In his half-an-inch 8x
telescope he saw it as being “like the obscured nucleus of a big comet.”
Messier could not find it in 1764 but
succeeded in 1778, describing it as “a nebula which is a whitish spot;
extending for 6' around the light is even and does not appear to contain a star.”
In the Philosophical Transactions, 1818,
William Herschel wrote: “1783, small 20 feet telescope. With 250 power
fairly resolved into stars; I can count a great many of them, while others are
too close to be distinguished separately. 1784, 1785, 20 feet telescope. A rich
cluster of very compressed stars, irregularly round, about 8' long.”
Dunlop 620 “a beautiful, large round
bright nebula, about 6' or 7' diameter, gradually condensed to the centre,
easily resolvable.”
h: “globular, pB, vL, R, vglbM, diam in
RA 30 seconds; all resolved into separate stars 13..16m, not so comp M as to run
together into a blaze or nipple.” On a second occassion he called it “globular,
a fine L, R, cluster, 6' diam, all clearly resolved into stars 11, 12, 13m, does
not come up to a nipple.”
Bailey, examining a Bruce plate (Harvard
Annals, Vol 72, No 2), describes it as “very remarkable, bright, globular
cluster, pretty compressed, several hundred faint stars, diameter15'.”
Hartung calls it “an open type of
globular cluster nearly 10' across, irregularly round, rising only broadly
towards the centre and beautifully resolved into stars scattered in a haze of
fainter ones. Even 3-inch will show this to be a cloud of faint stars.
Gore, observing with a 3-inch refractor in
India, saw “glimpses of stars in it with power 40X; it will not bear higher
powers with this aperture”.
Flammarion found it “plainly stellar... a
huge agglomeration of stars uniformly distributed and immersed in a pale
nebulosity. Diam. about 6' but a little elongated N-S This cluster should be
admirable in the southern hemisphere; for us it is a little pale.”
Burnham notes that “Early observers
commented on the unusual openness of this cluster, and found the centre to be so
little compressed that individual stars could be counted easily, with apparently
blank sky in-between. This impression is due to the fact that only a relatively
small percentage of the members exceed a brightness of 13th-14th magnitude, and
the cluster does not begin to “fill in” until one reaches about 17th
where a vast swarm of stars quite suddenly appears.
Stewart Moore (Fleet, Hampshire, UK),
observing with a 12-inch f/5, writes in the The Webb Society Nebulae and
Clusters Section Report No. 10, July 1992: “A difficult object to find.
Visible as a uniform grey patch about 10' in diameter. Not resolved even at high
power.”
Tom Lorenzin: “7M; 15' diameter; large
and distinct though faint; resolved but grainily with 12M and dimmer members;
little compressed center.”
Steve Coe, observing with a 13” f/5.6,
notes: “Bright, very large, irregularly round, very rich, somewhat
compressed, little brighter in the middle. I counted 67 stars resolved at 165X.
There are some dark lanes winding through the cluster.”
11x80: Wow! A giant globular
(at least 15’ across) with a broad nucleus. Dominates the field of view.
(exurban skies, moderate conditions) [AS]
8-inch Meade, 18mm eyepiece, 36.2’
fov: Large, very clear bright, roundish globular cluster, gradually
getting brighter to the middle with fringy edges. A haze of faint stars running
out to the far edges. This cluster did not resemble the frosted look but instead
a pale orange shade. About 15 arc minutes in size. (suburban skies) [MS] |
