M8 (NGC 6523)

M8 (NGC 6523) is The Lagoon Nebula, visible to the naked eye and a fine object in binoculars and small telescopes, perhaps the best example of an emission nebula.

This irregularly shaped nebula is twice the apparent size of the full moon. The brightest star here is 9 Sgr, a sixth-magnitude star slightly to the west of the nebula's centre.

The nebula is five degrees west of lambda Sagittarii: binoculars.

While binoculars will reveal dark lanes amongst the blue-green gaseous nebula, telescopes bring out many more features of this intriguing object.


Less than two degrees north is M20, the Trifid Nebula, which requires a large telescope and much time to fully enjoy.

John Herschel seems to have given the nebula its name, pointing out the three ‘bright and irregularly formed nebulous masses’ (quoting from Burnham, p1591).

One degree northeast of M20 is M21, an open cluster of about 57 stars; with an apparent magnitude of 6.5, it requires a small telescope to appreciate. While not as well known as the two nebulae to its southwest, this cluster deserves some attention—observers note such colourful stars as red, yellow, and blue. Quite young, with an age below 5 million years.

From M21 move one binocular field northeast to uncover mu Sagittarii

Click on mu Sagittarrii on the map to continue.

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