η Ophiuchi

Eta Ophiuchi is a white star which forms the southern-most point of the body of Ophiuchus: binoculars.

Eta is easily found with the naked eye. From delta Ophiuchi move southwest to zeta and then the same distance southwest to eta.

Eta is the multiple star system BU 1118 with mostly faint components (C through E are all 11 to 12 magnitude):
      AB: 3.1, 3.3; 235, 0.6", an orbit with a period of 88 years, presently at nearly its widest.

The double star BU 126 is in the same field of view: 6.3, 7.6; 263, 2.3".

Less than a degree southwest of this double star lies Messier's M9, a small but bright globular cluster with an apparent visual magnitude of 7.6; its brightest stars are only 13th magnitude. While one of the closest clusters to the Solar System at 19,000 light years away, the cluster is somewhat obscured by what is believed to be interstellar dust. Large binoculars show a tiny hazy circle; it takes a large telescope to resolve its central stars.

With eta centred drop due south two binocular fields to theta Ophiuchi.

Click on theta to continue.

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1999-2014 by Richard Dibon-Smith.