M16 - Eagle nebula
Messier 16 (M16), also known as the Eagle Nebula, is one of the most iconic and visually stunning star-forming regions in our galaxy. Here's a detailed overview :
Type : Emission Nebula and Young Star Cluster (open cluster)
Constellation : Serpens
Distance from Earth : ~7,000 light-years
Apparent Magnitude : 6.0 (just visible with binoculars in dark skies)
Size : About 70 × 55 light-years
M16 (NGC 6611) is a very young open cluster located in the tail of the constellation Serpens, near the constellations Sagittarius and Scutum. M16 is surrounded by the Eagle Nebula, designated IC 4703.
This nebula is locally referred to as M16, and there is some confusion between the two objects.
M16 was discovered by Swiss astronomer Jean Philippe Loys de Cheseaux in 1745, and the discovery of the nebula is attributed to Charles Messier.
According to Robert Trumpler's classification of open clusters, this cluster contains between 50 and 100 stars (letter m) whose concentration is medium (II) and whose magnitudes are distributed over a wide range (the number 3). The letter n indicates that M16 is bathed in a nebula. Note, however, that some sources indicate a number of stars greater than 8000 for M16, because of the confusion that exists between the cluster and the Eagle Nebula.
History
The open cluster was discovered by Jean-Philippe de Cheseaux in 1745. Charles Messier repeated this discovery on June 3, 1764, mentioning a cluster of stars "mixed with a faint light," suggesting the presence of a nebula around the cluster. The discovery of the Eagle Nebula is therefore attributed to Charles Messier, who listed it in his catalog under the designation M16, hence the confusion between the cluster itself and the Eagle Nebula.
William and Caroline Herschel observed the cluster in 1783, but they did not note the presence of the nebula. Consequently, the entry NGC 6611 in John Dreyer's catalog, based on Herschel's writings, is for the open cluster; it wasn't until 1908 that the Eagle Nebula was given the designation IC 4703.
The first photograph of the nebula was probably taken by Edward Emerson Barnard in 1895. More recently, images acquired by the Hubble Space Telescope in 1995 showed that the Eagle Nebula is a stellar nursery, in more scientific terms an HII region ; these spectacular images will remain among the most widely publicized from the space telescope and marked the beginning of a long series. In 2022, the James Webb Space Telescope imaged the nebula once again, revealing new details, with an ever-more precise image, and a new facade of M16, captured in infrared.
In astronomy, an ionized hydrogen region or H II region (read "H two") is an emission nebula consisting of clouds composed primarily of hydrogen, most of whose atoms are ionized, and sometimes extending over several light years.
HII regions get their name from the presence of large quantities of ionized hydrogen, denoted "HII". This is therefore the H+ ion, that is to say a simple proton, distinct from molecular hydrogen (H2) and atomic neutral hydrogen (HI).
Notable features
"Pillars of Creation"
The most famous part of M16, imaged by the Hubble Space Telescope.
These are towering columns of gas and dust where new stars are being born.
The "pillars" are massive — several light-years tall — and are sculpted by radiation and winds from nearby massive stars.
Star Formation
M16 is a stellar nursery. Inside the nebula, gravitational collapse of gas clouds leads to the birth of new stars.
The embedded open cluster (NGC 6611) powers the nebula’s glow, lighting up the surrounding gas.
How to Observe
Best Time to View : June to September
Location : In the "Serpent's Tail" region of the Serpens constellation.
Equipment : Visible with binoculars or small telescopes under dark skies. A telescope with a nebula filter will show more detail.
Professional Imaging : Often observed in infrared and X-ray to see through the dense dust.
Set up
Fra400 on Celestron AVX Mount
ASI533 MC Pro camera for imaging
ASI120 mini camera for guiding via OAG Celstron
Control via ASIAIR PLUS
Gain (ISO) : 101
Camera cooling : -10°C
Preprocessing and Processing : Pixinsight
The session
M16 was taken on June 22th, 29th & 30th 2025
41 images of 5 minutes each broken down as follows :
33 frames with the Antlia duoband (HO) 5 nm
8 frames with the Askar D2 (SO) 6 nm
Total integration : 3 hours 25
I did 2 processings :
A classic one using only the Antlia duoband (integration 2h45)
SHO - Hubble palette version using all the frames(integration 3h25)
I would have liked to do a little more frames but the target was very very low and the weather was quite capricious.
A lot of turbulence as the target moved toward the horizon.
The Final Images
SHO - Hubble Palette Version
Classic Version
Crop on the Pillars of Creation with a different processing under PixInsight
Processing in Hubble Palette
Astrometry : Annotated versions
Clear Sky !
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