In higher latitudes, the constellation Sagittarius unfortunately never rises particularly high over the horizon. It contains the center of the Milky Way as well as a variety of beautiful objects that can be observed during the summer months for a short time. The central region of the constellation with the stars ε, ζ, τ, σ, φ, λ, δ and γ is often interpreted as a teapot.
The 30 × 45 arcmin large Lagoon Nebula M 8 is clearly visible in binoculars, if the sky background is dark enough. The western part of the nebula is illuminated by the 6.0m bright star 9 Sagittarii, which is as bright as 1.6 million Suns. In the eastern part of the nebula you can see some stars of seventh to ninth magnitude which belong to the open cluster NGC 6530. Whether the 5,200 light-years distant star cluster is inside of the Lagoon Nebula or stands in front of it is still unclear because the distance measurement of nebulae is difficult.
M 17 also bears the names Omega-, Horseshoe- and Swan-Nebula. This 6,800 light-years distant gas cloud looks (especially in giant binoculars) similar to the number 2, but it can be seen in smaller binoculars, too. M 17 is sharply bounded on the north and west by dark clouds, while the other edges are less clearly defined. The dark cloud in its center is sometimes referred to as “fish‘s mouth“.
1° south of the Omega nebula is M 18, a rather inconspicuous open cluster with only nine minutes of arc in diameter, of which only the four brightest stars can be resolved in binoculars. The other stars of the 50 million years old star cluster blur to a weak shimmer. It is 4,100 light-years away and located in the space between two spiral arms of our galaxy, close to the Sagittarius-Carina arm.
The Trifid Nebula M 20 can be seen only under optimal conditions as a 30 arc minutes large, faint shimmer. The eponymous tripartite division is not visible in binoculars. The southern part of the nebula is an emission nebula and the actual Trifid Nebula. In the north it is connected to one of the few reflection nebulae that are bright enough to be visible in binoculars.
M 20 is located at the end of a complex of dark nebulae surrounding the Lagoon Nebula M 8. The stars of Webb‘s Cross are embedded into the Trifid Nebula – this small cluster of stars has emerged from the nebula and is today the power source that makes it fluoresce.
To the naked eye, Webb‘s Cross merges with M 21, a very young open cluster. About three dozen stars of M 21 can be resolved in binoculars. It has a diameter of 13 arc minutes and is about 5,200 light-years away.
The 10,000 light-years distant globular cluster M 22 is 5.1m and shows single stars in giant binoculars – at lower magnification it remains a rather bright patch of light. M 22 contains about 500,000 stars within 24 minutes of arc or 75 light-years. Since it never rises particularly high over the horizon from North America or Central Europe, it is relatively unknown, although it doesn‘t have to fear comparison with the 24,000 light-years away M 13. M 22 was identified by Abraham Ihle in 1665 as the first globular cluster.
It is still uncertain which object was really labelled M 24 by Charles Messier. Usually NGC 6603 is identified with M 24, but Messier‘s description fits better to the 1 × 2° wide Small Sagittarius Star Cloud. It appears as a large nebula with a variety of stars and is also noticeable to the naked eye. M 24 extends northeast of μ Sagittarii and is part of 12,000-16,000 light-years distant Norma spiral arm.
M 28 is almost 1° north of the 2.8m bright λ Sagittarii, which thus can be used for star hopping. The 19,000 light-years distant globular cluster contains about 100,000 stars and appears in the binocular as 15 minutes of arc large and 6.9m bright patch of light, in which no individual stars can be resolved. Its brightest stars only reach 14th magnitude.
In the southern part of Sagittarius, at the base line of the „teapot“, the three globular clusters M 54, M 69 and M 70 fit well into the field of view of binoculars – less than 5.5° separate M 54 from M 69. M 54 is the easternmost of the group. It is 1.5° west-southwest of the 2.6m bright ζ Sagittarii and appears as a 7.6m bright nebula. It is very dense and concentrated, and its diameter is only nine arcmin. At a distance of 85,000 light-years M 54 is not only the most distant globular cluster in Messier‘s catalog, but is also far beyond our galaxy. It belongs to the 80,000 light-years away Sagittarius Dwarf Spheroidal Galaxy, a satellite galaxy of our Milky Way, which plunges slowly into our galaxy. The dwarf galaxy has the luminosity of 33 million Suns, but it is distributed over a large area. Therefore, its compact globular clusters are easier to see than the galaxy itself, which remains reserved for photographs with long exposure times.
M 69 is a 33,580 light-years distant globular cluster and part of our galaxy, just like M 70. M 69 appears as a 7.5m bright nebula with a diameter of about seven minutes of arc and can’t be resolved into stars. Only four minutes of arc from the center shines a 8.0m bright foreground star – the stars of the globular cluster itself only reach 14th magnitude and can only be resolved in larger telescopes. M 69 can be found 2.5° northeast of ε Sagittarii.
M 70 lies 2.5° east of M 69 and offers a similar sight – with 7.9m, it appears only a little dimmer and more concentrated. It is 35,000 light-years away – only a little further than M 69, so that the two globular clusters also form a real couple in space.