BBC Sky at Night Magazine

Binocular tour

The Summer Beehive creates a buzz as it leads this month’s wide-field treasures

- With Steve Tonkin

1. The Summer Beehive

Let’s begin with a cluster that literally welcomes you to late spring skies. The Summer Beehive, IC 4665, is in the same field of view as Cebalrai (Beta (β) Ophiuchi) and contains curves of brighter stars that, rotated 90° anti-clockwise, form the word “HI”. This young open cluster is a pleasure in binoculars of any size and you should be able to resolve at least a dozen stars with your 10×50s.  SEEN IT

2. Poniatowsk­i’s Bull

We’ll continue with an easy object that seems to be made for binoculars – M186. It is centred on the 4th magnitude star 67 Ophiuchi and includes a prominent ‘vee shape’ made by 66, 67, 68, 70 and 73 Ophiuchi. This vee shape is reminiscen­t of the Hyades cluster in Taurus, a similarity that inspired the 18th-century Lithuanian astronomer, Marcin Odlanicki Poczobutt, to propose it as a new constellat­ion, Taurus Poniatovii (Poniatowsk­i’s Bull).  SEEN IT 3. M10 and M12

M12 is very close to the northeast apex of an equilatera­l triangle that has Yed Prior (Delta (δ) Ophicuchi) and Zeta (ζ) Ophiuchi as its other apexes; M10 is a little more than 3° southeast of it. They offer a useful demonstrat­ion of averted vision: if you mount your binoculars, you will find that when you direct your gaze to one, the other brightens. This will also show that M10 has a much more distinct core.  SEEN IT

4. Psi (ψ) Serpentis

Psi (ψ) Serpentis is easy to locate as it is due south of Unukulhai (Alpha (α) Serpentis) and west of Omega (ω) Serpentis. Initially you’ll see a pair of yellow stars 6 arcminutes apart but, as you look more carefully, you should be able to make out a third, much fainter, star mid-way between them. This is a line-of-sight grouping; the brightest star is much closer than the others and is only 5% as luminous.  SEEN IT 5. M5

Our next target is another globular cluster, M5, which is 6° due west of ψ Ser and next to a 5th magnitude star, 5 Serpentis. This 24,500 lightyear-distant cluster is one of the largest known globulars. It spans 165 lightyears and is estimated to house close to half a million stars. These are metal-poor Population-II stars that formed about 13 billion years ago, at the same time as our Galaxy.  SEEN IT

6. Harrington 7

Our next target was discovered by well-known binocular aficionado, Phil Harrington. Identify Kajam (Omega (ω) Herculis) and pan 2° west to a golden 8th magnitude star, part of a 1.3°–long chain of fainter stars that runs north to south. It is pareidolia, where familiar pictures are seen as random patterns. Harrington describes it as a zigzag. What do you see?  SEEN IT


Tick the box when you’ve seen each one

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