There are two pictures of the Lagoon Nebula shown below. The first is a color image showing just a part of the nebula and cluster. The second is a wide-field black & white picture that shows more of the nebula and cluster.
CCD image taken with an ST-1301E CCD camera thru our 20-inch telescope working at around F/5. This image is made from 10 minute exposures thru red, green, and blue filters. The field of view is about 20x20 arc minutes with North at the top. This image only shows a portion of the nebula and cluster.
This is a mosaic of two 10 minute exposures using a red filter. The mosaic shows the entire cluster, but still only a portion of the nebula. The red filter brings out the details in the cluster that glows bright red because of its ionized hydrogen gas.
John Flamsteed: (1680) 'A "nebulosum" in front of the Bow of Sagittarius.'
Philippe de Cheseaux: (1746) 'A star cluster in Sagittarius' Bow.'
Guillaume Le Gentil: (1747) 'A small nebulosity like the tail of a comet with numerous stars....... Like the more transparent and whitish localities of the Milky Way.'
Charles Messier: (May 23rd, 1764) 'A cluster which looks like a nebula in an ordinary telescope of 3 foot focal length, but in a good instrument on observes only a large number of small stars. A fairly bright star nearby is surrounded with a very faint glow……'
M-8, "The Lagoon", is a bright nebula, with an associated star cluster, in the Constellation Sagittarius. It is divided by a dark lane, and there are other embedded dark areas; it extends over a patch of sky 3 x 1.3 times the apparent diameter of the Moon. M-8 is easily visible in the smallest of telescopes, and from a dark location one can see it without any optical aid. The redness of the surrounding emission nebula gas is caused by electrons recombining with hydrogen nuclei, while the dark regions are dust lanes that absorb light from background sources. Within the brightest part of the Lagoon is a figure-eight feature known as the Hourglass Nebula (see HST images), discovered by John Herschel and associated with a number of hot young stars, including Herschel 36 (magnitude 9.5, spectral type O7). Close to this feature is the brightest star associated with the Lagoon Nebula, 9 Sagittarii (magnitude 5.97, spectral type O5), which contributes much of the ultraviolet radiation that causes the nebula to glow. One of the most remarkable features of the Lagoon is the presence of dark globules that are thought to be collapsing proto-stellar clouds.
George Normandin, KAS
September 5th, 2006