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Icon 51: Cassiopeia OB8
Cassiopeia is a very interesting Autumn and Winter constellation. This constellation has many deep-sky targets to offer. Even without a star chart, chances are that you run into several open clusters while scanning that part of the Milky Way with a pair of binoculars. One of the most enjoyable star fields can be seen near Delta and 44 Cassiopeiae. Here you will find a few members of the so called Cassiopeia OB8 Association: M103, NGC663, NGC654 and NGC 659. All these clusters can be seen in one single field of view. The OB8 association is thought to be 20 to 25 million years old and 9.200 l-y away. For the easy of orientation in this crowded window of our home galaxy, I included a labelled sketch as well. M103 can be found at 1° ENE of Delta Cas. It is a rather compact and inconspicuous streak of light. Only 3 stars are visible. Continue for another 1,5° further away from Delta and you’ll encounter NGC 663. At first, I noted two pairs of brighter stars at the N edge of a triangular patch of light. With averted vision, more fainter stars can be resolved. A dark lane, running from N to S through the cluster, seems to separate the two pairs brighter pairs of stars. NGC 654 is a small fan shaped glow, at 40’ NNW of NGC 663. A bright mag 7.3 star marks its SE border. A true resolution of this dense cluster was not possible. The weak glow of NGC 659 can be seen with averted vision. This little cluster is located right next to 44 Cas and in the direction of NGC 663. It was my impression that I could see 4 faint stars embedded in a faint patch of light.
Site : Bekkevoort, Belgium ( 51° N )
Date : November 25, 2008
Time : around 21.30UT
Binoculars : TS Marine 15x70
Filter : none
Mount : Trico Machine Sky Window
Seeing : 2/5
Transp. : 3/5
Sky brightness : 19.64 magnitudes per square arc second near zenith (SQM reading).
Sketch Orientation: N up, W right.
Digital sketch made with Corel Paint Shop Pro X2, based on a raw pencil sketch.
(Note: if the sketch does look too dark on your monitor, try to darken the room.)
|Name:||Rony De Laet|