Binocular tour

V-shaped star clusters and rich star fields are among June’s wide-field highlights

1 The Summer Beehive (10x50)

The Summer Beehive (IC 4665), looking like a smaller version of Praesepe (the Beehive Cluster), welcomes you to the summer skies: look for the curved chain of white stars which forms part of the letter ‘H’ of the inverted word ‘HI’. This large young (40 million years old) cluster is delightful in binoculars of any size. You should be able to resolve a dozen stars with a pair of 10x50s. SEEN IT

2 Poniatowski’s Bull (10x50)

We’ll continue with another easy object; one that is better in wide-field binoculars than any other instrument. Poniatowski’s Bull (Melotte 186) is a 4° diameter open cluster that includes the V-shape formed by 66, 67, 68, 70 and 73 Ophiuchi. These 4th and 5th magnitude stars lend it a similarity to the Hyades cluster in Taurus, hence its common name, given in honour of an 18th-century king of Poland. SEEN IT

3 NGC 6633 (10x50)

If you follow the left-hand leg of the V-shaped asterism in from Mel 186 a further 5.5° to the northeast, you should find NGC 6633. This pretty cluster is easily visible in a pair of 10x50s with the four brightest stars shining against the 20 arcminute elongated glow of the unresolved fainter cluster stars. If you compare it to the Summer Beehive, you will see that its stars are yellower, and therefore older. SEEN IT

4 Graff’s Cluster (10 50)

From NGC 6633, pan 3° in the direction of mag. +4.6 Alya (Theta Serpentis), and find the 1° diameter soft glow of Graff’s Cluster (IC 4756). This cluster is over 20 lightyears across and around 1,300 lightyears away. It rewards patient observation: try averted vision on it and you may experience it as being ‘brighter stars, scattered over a background of diamond dust’. SEEN IT

5 NGC 6572 (15x70)

NGC 6633 lies almost exactly between Graff’s Cluster and this month’s challenge, planetary nebula NGC 6572. At mag. +8.1, it’s easily bright enough to be visible, but less easy to identify, so use the inset finder chart. Once you have identified it, see if you can detect any colour; you may detect a hint of green or blue (which colour appears to be agedependent) with direct vision. SEEN IT

6 The Scutum Star Cloud (10x50)

Let’s conclude with the rich star field that occupies the northeast quarter of Scutum. It’s easy to find and has been mistaken for a cloud on a clear night. There seem to be ripples of stars, formed by the indistinct dark nebulae that weave through it. You should also see the stars that form the open cluster M11, called the ‘Wild Duck’ due to its V-shape. SEEN IT Tick the box when you’ve seen each one