Messier 23
From DeepSkyPedia
| M 22 << Messier 23 >> M 24 Cr 355 << Collinder 356 >> Cr 357 Mel 183 << Melotte 184 >> Mel 185 | |
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| Position (epoch J2000) [1] | |
| Constellation | Sagittarius |
| Position | Ra 17:57:04.7 Dec -18:59:07 |
| DSS images | |
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Appearance [1] | |
| Apparent mag. | 5.5 |
| Size | 30' |
| Class | II 2 r |
| Stars | |
| Dreyer's description | Cl B vL pRi lC st 10... |
| Other | |
| Other designations | M 23, NGC 6494, Collinder 356, Cr 356, Melotte 184, Mel 184, Lund 793 and ESO 589-SC022 |
| Notes | |
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Messier 23 is an open cluster in Sagittarius.
[edit] How to find it
[edit] Appearance
The brightest part of the cluster covers the area of 15'x25'. The brightest star in the area is 8.3-mag HD 163536 (not a member!). There are no stars in the cluster brighter than m=9.3, but more than 20 stars fall in 9.3 to 10 magnitude range!
Many stars are arranged in chains, which becomes visible as soon as few tens of stars are resolved.
[edit] Naked eye
Given its visual magnitude of 5.5, it propably can be detected with naked eye[Citation needed].
[edit] Telescopes up to 70mm, binoculars up to 50 mm, and finders
It can be detected with 7x35 binoculars even under 4.5-mag skies.[2] Under 5.0-mag skies, in 7x35, the cluster looks large and diffuse. No stars can be resolved at this power.[3]
Binoculars 10x50 binoculars will make it brighter, but the power of 10x will propably be to low to resolve any stars.[2]
[edit] Telescopes 71mm - 100mm (2.8" - 3.9"), binoculars 51mm - 70mm
In 80-mm refractor or 20x70 binoculars, cluster looks large, oval-shaped and dense.
Power of 20x (like in 20x70 binoculars), will be enough to finaly bring out individual stars and show dense open cluster.[2] Increasing power to 31x (80 mm scope) brings out many faint stars in the background.[4]
At higher power, like 71x, under 7.1-mag skies, a few tens of stars can be seen in the cluster.[5]
[edit] Telescopes 101mm - 141mm (4" - 5.5"), binoculars 71mm - 100mm
In 110mm or 120mm scope, under very dark skies (LM between 6.5 and 7), at lower power (28x), 45 to 50 stars are visible inside 25'x15' ellipse. The stars are moderately bright, and almost all are of the same brightness.[6]
At moderate power, at least 50 (53x)[6], with many star-chains, can be seen. Under very dark skies (LM=7.0), up to 70 stars[7] can se resolved!
More reports:
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Messier 23 observation and sketch by Rony De Laet with Meade ETX 105 [include this report]
- M 23 with 4.5" (114mm) f/8 homemade dobson (babydob) by Ante Perković (SEEN, Aug 04 2003) [include this report]
- M 23 with 25x100 binoculars by Ante Perković (SEEN, May 06 2005) [include this report]
[edit] Telescopes 141mm - 177mm (5.6" - 6.9")
A 6" telescopes will make cluster brighter, but number of visible stars will rise (compared to smaller telescopes) very slowly. Stars are of almost equal brightness.[8]
More reports:
[edit] Telescopes 178mm - 234mm (7" - 9.2")
In 8" telescopes, (at 63x[9] to 111x[10]), M 23 is large, loose, cluster of cca 55 stars. Several chains of stars can be seen meandering through the cluster.[10]
[edit] Telescopes 235mm - 305mm (9.25" - 12")
In 10" telescopes, cluster is very bright and impressive, even at low power (44x). There is not much very faint stars so averted vision doesn't help much.[11]. At 80x, cca 50 - 55 stars can be resolved.[12]
More reports:
- Messier 23 observation by David Erzeel @ deepskylog.be (with Sky-Watcher 10" dobson (250 mm)) [include this report]
[edit] Telescopes 306mm - 381mm (12.1" - 15")
- Messier 23 observation by Paul Kemp (Southern Sentinel) with 13.1" f/5 Dobsonian (22nd July 2006) [include this report]
- Messier 23 observation by Paul Kemp (Southern Sentinel) with 13.1" f/5 Dobsonian (114x) (16th June 2007) [include this report]
- Messier 23 observation by Jeff Burton (x.astrogeek.org) with AstroSystems TeleKit 14.5" Reflector [include this report]
[edit] Telescopes above 15"
[edit] Notes
[edit] References
- ↑ 1.0 1.1 Historic NGC and IC by Wolfgang Steinicke (version Nov. 20, 2006.)
- ↑ 2.0 2.1 2.2 x.astrogeek.org , Jeff Burton , Bushnell Falcon 7x35mm Binoculars, Bushnell GlassesOn 10x50 Binoculars, Oberwerk FMC Mini-Giant 12x60mm Binoculars , May 15, 2001 , Paducah, KY, USA , LM: 4.0 - 4.5 , seeing: 8/10
- ↑
mdangel.net: Messier 23 , Matt Dangel , ?x , 06-08-1996 , Sherman, Texas , LM: 5.0 - ↑ x.astrogeek.org , Jeff Burton , Celestron Wide View 80mm Refractor , 31x , October 25, 2003 , Pennyrile State Park, KY, USA , LM: 5.8 , seeing: Antoniadi: II/III
- ↑
M 21 (sketch and report) , Jaakko Saloranta , Refractor Konus , d=3" , f=3" , 67x , 18./19.4.2004 , ase del Teide, Tenerife, Spain , LM: 7.1 , seeing: 2
- ↑ 6.0 6.1 with 120mm f/8.33 refractor, eq. mount (Konus, Lukrica) by Ante Perković (SEEN, Jul 17 2004) [include this report]
- ↑
Messier 23 (sketch and report) , Iiro Sairanen , TAL-1 Newton , d=110mm , f=110mm , 64x , 118/19.4.2004 , Base del Teide, Tenerife, Spain (2280m) , LM: 7,0
- ↑ Sagittarius by Steve Coe - M 23 , Steve Coe , 6" f/6, 13.1" f 5/6 , 75x, 100x
- ↑
Messier 23 (sketch and report) , Jere Kahanpää , Newton , d=205mm , f=205mm , 63x , 6./7.8.1992 , Öland, Sweden , LM: 5.8 , seeing: 3
- ↑ 10.0 10.1 x.astrogeek.org , Jeff Burton , Meade LX200GPS 203mm SCT , 111x , June 16, 2002 , Paducah, KY, USA , LM: 5 , seeing: 9/10
- ↑ (IAAC) M23 (NGC 6494) , Mitchell Diers , Dobsonian , d=10" , f=45" , 44x, 118x, and 178x , June 11, 2002 , Turlock, CA, USA
- ↑
Messier 23 (sketch and report) , Juha Ojanperä , Newton , d=250mm , f=250mm , 80x , 4/5.9.2007 , Parainen, Finland , LM: 6.2 , seeing: 3
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