Messier 23 - NGC 6494

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Bode 42, h 1990, GC 4346, Melotte 184, Mel 184, Collinder 356, Cr 356, C 1753-190

Type  Open Cluster
Magnitude  5.5
Size  27'
Right Ascension  17h 57' 4.8"  (2000)
Declination  18° 59' 7" S
Constellation  Sagittarius
Description  Cl, B, vL, pRi, lC, *10..
Classification  III 1 m
Observing Notes

Andrew Cooper
Jun 1, 2022    Waikoloa, HI (map)
20cm f/6 Newtonian, Cave Astrola @ 76x
Seeing: 7 Transparency: 6.5 Moon: 0%

A bright large cluster in a rich galactic starfield, rich, coarse, fully resolved, a notably clumpy appearance with similarly notable voids, 25' in diameter with stars of 9th to 12th magnitude

Andrew Cooper
Sep 16, 2020    Waikoloa, HI (map)
20cm f/6 Newtonian, Cave Astrola @ 76x
Seeing: 6 Transparency: 7 Moon: 0%

Big! Bright! a splendid cluster in a rich galactic starfield, about 30' in diameter, rich, resolved, several hundred 8-12th magnitude stars arranged in notable chains and clumps, three notable chains run from northwest to southeast across the main body of the cluster, the 6.5 magnitude star HR6679 on the northwest margin, the 8.3 magnitude HD163536 in the northeastern reach

Andrew Cooper
Jun 27, 2020    Waikoloa Quarry, HI (map)
8x42mm Nikon Prostaff 3S Binoculars @ 8x
Seeing: 7 Transparency: 7 Moon: 0%

A conspicuous cluster one field north of M8 and M20, large, bright, not resolved, about 15' in diameter

Andrew Cooper
Jun 11, 2010    Hale Pohaku, HI (map)
46cm f/4.5 Newtonian, Deep Violet @ 60x
Seeing: 8 Transparency: 7.5 Moon: 0%

Large! Bright! a coarse cluster with a couple hundred members arranged in conspicuous chains and clumps across a 30' region

Andrew Cooper
Apr 18, 2010    Hale Pohaku, HI (map)
46cm f/4.5 Newtonian, Deep Violet @ 60x
Seeing: 6 Transparency: 7 Moon: 0%

Large! bright, a coarse cluster spanning over 25', 80-100 9th and 10th magnitude stars arranged in arcs and chains throughout the area

Andrew Cooper
Mar 14, 2010    Hale Pohaku, HI (map)
15cm f/5 Newtonian, Primero @ 55x
Seeing: 7 Transparency: 6.5 Moon: 0%

Large! Bright! bright an loose cluster over across, a few dozens of stars scattered in a half degree patch, nice object for the 6" RFT

Andrew Cooper
May 25, 2006    Gila, NM (map)
9x63 Binoculars

Easy binocular object, a hazy patch just beginning to resolve, very distinct from the Milky Way star field

Andrew Cooper
May 25, 2006    Gila, NM (map)
46cm f/4.5 Deep Violet

Large!, loose and coarse, bright, several hundred stars in a 30' area, many of the stars arranged in short arcs

Rev. T.W. Webb
May 19, 1885    Hardwick, Herefordshire, England (map)

Grand low power field. h., about 100 stars, 9-10 mg to 13 mg. Announced by increasing number.
― Celestial Objects for Common Telescopes, T. W. Webb, 1917

Captain William Henry Smyth
Jul 17, 1835    No. 6 The Crescent, Bedford, England (map)
150mm f/17.6 refractor by Tully 1827

A loose cluster in the space between Ophiuchus's left leg and the bow of Sagittarius. This is an elegant sprinkling of telescopic stars over the whole field, under a moderate magnifying power; the most clustering portion is oblique, in the direction sp to nf, with a 7th-magnitude star in the latter portion. The place registered it that of a neat pair, of the 9th and 10th magnitudes, of a lilac hue, and about 12" apart.

This object was discovered by Messier 1764, and it precedes a rich out-cropping of the Milky Way. The place is gained by differentiating the cluster with μ Sagittarii, from which it bears north-west, distant about 5°, the spot being directed to by a line from σ on the shoulder, through μ at the tip of the bow.

After having examined this object, I lowered the telescope a couple of degrees, and gazed for the curious trifid nebula, H IV 41; but though I could make out the delicate triple star in the centre of its opening, the nebulous matter resisted the light of my telescope, so that its presence was only indicated by a peculiar glow. Pretty closely preceding this is No. 20 M., an elegant cruciform group of stars, discovered in 1764, which he considered to be surrounded with nebulosity.
― A Cycle of Celestial Objects Vol II, The Bedford Catalogue, William Henry Smyth, 1844

William Herschel
Jun 18, 1784    19 New King Street, Bath (map)

A cluster of beautiful scattered, large stars, nearly of equal magnitudes (visible in my finder), it extends much farther than the field of the telescope will take in, and in the finder seems to be a nebula of a lengthened form extending to about half a degree.

Charles Messier
Jun 20, 1764    

A star cluster, between the end of the bow of Sagittarius & the right foot of Ophiuchus, very near to 65 Ophiuchi, according to Flamsteed. The stars of this cluster are very close to one another. Its position was determined from Mu Sagittarii.
― Connaissance des Temps, 1781

Charles Messier
Jun 20, 1764    18.5" reflector @ 350x

In the night of June 20 to 21, 1764, I determined the position of a cluster of small stars which is situated between the northerb extremity of the bow of Sagittarius & the right foot of Ophiuchus, very close to the star of sixth magnitude, the sixty-fifth of the latter constellation [Oph], after the catalog of Flamsteed: These stars are very close to each other; there is none which one can see easily with an ordinary [non-achromatic] refractor of 3 feet & a half, & which was taken for these small stars. The diameter of all is about 15 minutes of arc. I have determined its position by comparing the middle with the star Mu Sagittarii: I have found its right ascension of 265d 42' 50", & its declination of 18d 45' 55", south.
Other Data Sources for Messier 23
Associated objects for Messier 23
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Messier 23