What we see as the Lagoon Nebula in photographs is a far larger and more complex region than what visual observers could see when the Nebula was first observed in the 17th through 19th centuries. As a result, there are several NGC entries corresponding to different parts of the Nebula, and who should be credited with the discovery of which part of the Nebula is less than perfectly clear. The link to NGC 6533 is used simply because it is currently the most detailed of the NGC entries involved, and that identification should be considered tentative until further notice.

M16 consists of the star cluster (NGC 6611) which illuminates the Eagle Nebula (IC 4703), and (particularly in modern usage) the Nebula itself. Given the double listing in the NGC/IC and the difficulty of knowing exactly what historical observers saw or thought they saw, it is sometimes listed as only the cluster or only the nebula, and sometimes as the combination of the two. As a result, as in the case of M8, this entry and its associated NGC/IC entries need considerable work before they can be considered more or less definitive, and the entry is subject to revision until further notice.

M78 (= NGC 2067 and 2068) is the bright nebula crossed by a semi-circular arc of obscuring material near the center of the image below. For NGC catalog purposes, M78 is divided into two parts. The brighter region, framed by the dark dust lane surrounding the left portion, is NGC 2068. The fainter region to the right of the dust lane is NGC 2067. The reflection nebula at the top of the image is not considered part of M78, and is referred to as NGC 2071.