NGC 6530 was classified as of Trumpler type «II 2 m n» (see e.g. the Sky Catalog 2000), meaning that it is detached but only weakly concentrated toward its center, its stars scatter in a moderate range of brightness, it is moderately rich (50 — 100 stars), and associated
with nebulosity (certainly, with the Lagoon nebula).
The IC description, «extremely large cloud of stars
with nebulosity», would at least match with the appearance of M24.
The young open cluster NGC 6530 associated with the Lagoon Nebula M8 was classified as of Trumpler type «II 2 m n» (see e.g. the Sky Catalog 2000), meaning that it is detached but only weakly concentrated toward its center, its stars scatter in a moderate range of brightness, it is moderately rich (50 — 100 stars), and associated
with nebulosity (certainly, with the Lagoon nebula).
While Méchain found it to be a nebula without stars, Messier thought it was composed of small stars
with some nebulosity, probably being fooled by foreground or background stars.
Not exact matches
Elsewhere in the image, we can look into Orion A's dark molecular clouds and spot many hidden treasures, including discs of material that could give birth to new stars (pre-stellar discs),
nebulosity associated
with newly - born stars (Herbig - Haro objects), smaller star clusters and even galaxy clusters lying far beyond the Milky Way.
Astrophotograph of M31, also known as the Andromeda nebula, taken using an 85 mm telescope
with a hydrogen - alpha filter to enhance
nebulosity (Photo: Adam Evans)
This giant cloud, or complex of clouds, of interstellar matter and young stars contains, besides M42 and the neighboring DeMairan Nebula (M43), and the
nebulosity associated
with them (NGC 1973-5-7), a number of famous objects, including Barnard's Loop, the Horsehead Nebula region (also containing NGC 2024, or Orion B), and the reflection nebulae around M78.
In my 32 mm eyepiece
with a true field of view of 46 ′, the cluster and the
nebulosity lie at the end of an S - shaped asterism of stars, which can be identified easily.
Already under fairly good conditions, the nebula itself can be glimpsed
with the naked eye as a faint
nebulosity around this star.
I know that Usoskin et al. have recently suggested a latitudinal dependence of
nebulosity - CR relationship,
with strongest correlations observed over 20 - 55 ° S and 10 - 70 ° N. I guess that cosmic ray intensity could varies over the globe in relation to geomagnetic field.