NGC 1931
Typ: Open Cluster (OCL 441, Cr 68, St 9) + Emission Nebula (LBN 810, Sh 2-237)
RA: 05h 31m 26s
DEC: 34° 14' 42"
Size: 6'
Mag: 10.1 vmag

Parsamian 1
Typ: Reflection Nebula
RA: 05h 31h 04s
DEC: 34° 11' 00"
Size: 1.1'

Just 1° west of Messier 36, or just NE of the more famous IC 405/410 complex we could find a nice and bright nebula with a beautiful embedded open cluster, all named NGC 1931.

In 1793, Wilhelm Herschel first noticed the nebula and the cluster and described the object as "very bright, large, round, bright triple star in middle". The smaller reflection nebula Parsamian 1 only 4' south was first mentioned by the Armenian astronomer Elma Parsamian. Working at the Byurkan Astrophysical Observatory (BAO) she searches after cone shaped nebula and listed 23 objects.

From the astrophysical aspect, both objects belongs to the Auriga OB1 association. The view goes through the "Auriga window" trough the galactic anticenter and allows us a deep and distant look in the outer regions of our galaxy. Bhatt et al [1994BASI...22..291B] gives a distance of around 7000 ly. The SOS [10.1088/0004-6256/149/4/127] confirm this distance and give an age of 2 Myr to the young cluster. To sum up, our objects are located in the space between our local Orion Arm and the more distant Perseus Arm. It is flanked by the nearer IC 405 (1500 ly) and the more distant IC 410 (12000 ly).

But what makes NGC 1931 so interesting in the telescope. First the nebula, which is often called the "mini-Orion nebula". The relative bright centre of around 3' is already visible in smaller telescopes. Because of the combination of reflection and emission parts, the nebula is already visible without any filter. UHC filters don't bring a massive effect and let the nebula shining equally bright. The open cluster inside is dominated by a very small (10") equilateral triangle of stars of around 11mag. Larger telescopes could verify the cluster character by showing the much fainter stars of the cluster just south of the triangle. Parsamian 1 is much fainter but doable in mid size telescopes. His shape is running from E to SW, starting from an 11mag variable star.

picture Bernhard Hubl, 12", LRGB
N1931-1.jpg
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sketch Uwe Glahn, 27", 293x, NELM 7m0+, Seeing IV
NGC1931.jpg
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