ε Sagittarii

Epsilon Sagittarii, ‘Kaus Australis’, The Southern Part of the Bow, marks the end of the bow as held by the Archer. This blue-white giant is the brightest star in the constellation, with a visual magnitude of 1.8.

To find epsilon, with the trapezoid fully in your glasses move southwest a bit more than one and a half fields of view: binoculars.

In this field are two Messier objects, M69 (7.6m) and M70 (8.0m), both of which are quite small globular clusters, needing large scopes to enjoy.


Southwest of epsilon one binocular field is the equally bright red giant eta Sagittarii, which looks more orange than red. Its radius is 57 times that of the Sun.

Eta is a binary (BU 760)AB: 3.3, 8.0, 100º, 3.6" with an orbit of over 1250 years.

In the same field, directly west of eta Sgr, is the binocular multiple star system DUN 219:
      AB: 5.9, 7.8; 252º, 53.5".
      AC: 5.9, 11.3; 175º, 40.1".

Returning to epsilon, five degrees north of epsilon is delta, and about a binocular field west of delta is gamma, el Nasl or Alnasl, The Point, as it denotes the tip of the arrow the Archer is aiming.

Surprisingly there are no Messier objects in this binocular field of view, but there is a nice binary, h5003, just west of gamma—two red stars, AB: 5.4, 7.0; 103º, 5.5".

The central star in this field is W Sagittarii, a very bright Cepheid variable which fluctuates between 4.3 and 5.1 magnitudes every 7.59 days. The star is also a binary with two 13.5m companions.
     In some references W Sagittarii goes by the name gamma1, with gamma Sagittarii then called gamma2. But as the two stars are not bound gravitationally to each other, there seems little reason to follow this practice.

We'll cross into Corona Australis to find alpha Sagittarii; with epsilon Sagittarii centred move two binocular fields southeast and you will find the ‘southern crown’ nicely framed in your glasses. Now a little more than one binocular field southeast brings in alpha and beta Sagittarii.

Click on alpha on the map to continue.

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