Open Cluster Messier 18

Messier 18
Messier 18: Section of STScI Digitized Sky Survey [147]

Object Description

About one degree south of the magnificent galactic nebula M 17 les the small open star cluster Messier 18. It was discovered on June 3, 1764 by Charles Messier, who described it as a cluster of small stars surrounded by a little nebula. This impression of nebulosity is caused by numerous fine background stars, which are too faint to be resolved. Modern recordings, however, show a delicate hint of a nebula surrounding the pile, but this is far too faint for Messier to detect with his rather modest instruments.

M 18 is one of the neglected Messier objects and is often not included in lists of galactic star clusters. The distance is given as about 4900 light years. [4]

«Revised New General Catalogue and Index Catalogue» Dr. Wolfgang Steinicke, 2021 [277]
DesignationNGC 6613
TypeOCL (II3pn)
Right Ascension18h 19m 58.0s
Declination-17° 06' 06"
Diameter7.00 arcmin
Visual magnitude6.9 mag
Dreyer DescriptionCl, P, vlC
IdentificationM 18, OCL 40

Finder Chart

M 18 is located in the constellation Sagittarius, roughly in the middle between the Omega Nebula (M 17) and the Small Sagittarius Cloud (M 24). Connect the two stars Kaus Borealis (λ Sagittarii) and γ Scuti. Position the Telrad west of it so that the outermost Telrad circle is on the line.

Chart Messier 18
Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

References

4«Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System» by Robert Burnham; Dover Publications, Inc.; Voume I: ISBN 0-486-23567-X; Volume II: ISBN 0-486-23568-8; Volume III: ISBN 0-486-23673-0
147Aladin Lite; aladin.u-strasbg.fr/AladinLite (2020-12-23)
149SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
160The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; klima-luft.de/steinicke (2021-02-17)