Zeta Orionis (Alnitak)

ϑ1 and ϑ2 Orionis
Theta1 Orionis is a celebrated multiple star system in the middle of The Orion Nebula, a cluster which goes by the name of ‘The Trapezium’.
      It is the illumination provided by these multiple members of theta Orionis that the nebula has become one of the most popular in the heavens.
      If you centre the Belt and move one field south, then the nebula and the The Trapezium will be centred: binoculars, just above the brighter iota, 2.75 magnitude.

The Trapezium (ϑ1A, ϑ1B, ϑ1C, and ϑ1D) can be seen in binoculars but a telescope brings in more members of the group: Trapezium. (The object is upside down to reflect the aspect that most telescopes present.):
       AB: 6.6, 7.5; 31º, 8.9".
       AC: 6.6, 5.1; 132º, 12.7".
       AD: 6.6, 6.4; 96º, 21.4".

The ϑ1 system also forms an optical binary with ϑ2; the companion is a very wide 135".

ϑ2 Orionis is a multiple binary in its own right (Struve Appendix 16):
       AB: 5.0, 6.2; 93º, 52.0".
       AC: 5.0, 8.5; 58º, 128.0".

Iota Ori, in the same region, is also a multiple system (Struve 752):
      AB: 2.8, 7.7; 141º, 11.6".
      AC: 2.8, 9.8; 103º, 49.4".

On the eastern edge of this binocular view is Struve 790, a yellow primary and blue companion: 6.4, 9.0; 89º, 7.1".

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