Sky & Telescope - July 2021 - 32

Imaging Star Clusters

S EXTRATERRESTRIAL CLUSTER NGC 4326 (top right) and NGC
457 (lower left) make a nice pair in wide-field instruments. Though often
referred to as the Owl Cluster, NGC 457 is sometimes called the E.T.
Cluster. It particularly resembles the fictional movie character complete
with an outstretched, overly long left arm if you rotate the image so that
the bottom left corner is at top.
X DISTANT GLOBULAR Top: NGC 2419 is one of the most distant
globular clusters associated with the Milky Way, residing roughly 300,000
light-years from Earth and from the galactic center.
X STAR FACTORY Right: The Orion Nebula, M42, is the nearest starforming region and contains one of the youngest star clusters nearest
to Earth: the Trapezium, also known as θ Orionis. Two other bright
clusters are seen in near proximity, including NGC 1980 (bottom) and
NGC 1981 (top).

Another clutch of hot, young stars lies at the heart of
M42, the Orion Nebula. Short exposures in very steady seeing
resolve the six primary stars of the Trapezium (θ Orionis) still
ensconced in their nebulous womb, M42. Short exposures
reveal both θ Orionis and the inner clouds of gas and dust
nearest to the young cluster. To reveal the faint extensions
in the surrounding molecular cloud, it's best to combine short
and long exposures - ranging between 30 seconds and 10
minutes - using High Dynamic Range (HDR) image-processing techniques. Several other open clusters are found within
2° of the Orion Nebula. Just 1° north is NGC 1981, a widely
spaced open cluster with hot, blue stars arrayed in a distinct W
shape. In the opposite direction (½° south of M42), NGC 1980
is even brighter and includes several naked-eye stars.
Skipping up to Auriga, we find M36, M37, and M38, a
trio of great open clusters. Of the three, I find M37 the most
32

J U LY 2 0 2 1 * S K Y & T E L E S C O P E



Sky & Telescope - July 2021

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