Our roundup of wide-field gems includes the Summer Beehive and Barnard’s Star
1. The Summer Beehive
Recommend equipment: 10×50
The Summer Beehive (IC 4665), looks like a slightly smaller version of Praesepe (the Beehive Cluster) and, with its curved chain of white stars that form part of the letter ‘H’ in the inverted word ‘HI’, welcomes you to the summer skies. This relatively young cluster is a delight in binoculars of any size and you should easily be able to resolve 10 or more stars with a pair of 10x50s.
2. Poniatowski’s Bull
Recommend equipment: 10×50
We’ll continue with another easy object, one that looks better in wide-field binoculars than any other. 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 make it similar to the Hyades cluster in Taurus, hence its common name, given to it in the 18th century in honour of Stanisław Poniatowski, King of Poland.
3. Graff’s Cluster and NGC 6633
Recommend equipment: 10×50
Our next target is a pair of contrasting clusters. Follow the left-hand leg of the V-shaped asterism of Melotte 186 a further 5½° to the northeast to find NGC 6633, with its four brightest stars glinting against the 20-arcminute gleam of the unresolved stars. If you now pan 3° towards mag. +4.6 Alya (Theta (θ) Serpentis), you will find the 1° diameter glow of Graff’s Cluster, IC 4756.
4. Barnard’s Star
Recommend equipment: 15×70
This veritable Skies’ has the greatest proper ‘Greyhound of the motion (apparent motion relative to the celestial sphere). To find it, identify mag. +4.8 star 66 Ophiuchi, and use the inset chart, above. It only shines at mag. +9.5, so it can be a challenging target in summer skies that don’t get properly dark. Using binoculars, it will take you about a decade to detect its apparent motion of 10.3 arcseconds a year.
5. M10 and M12
Recommend equipment: 10×50
M12 is close of an equilateral triangle that has to the northeast apex mag. +2.7 Yed Prior (Delta (δ) Ophiuchi) and Zeta (ζ) Ophiuchi as its other apexes; M10 is about 3° southeast of it. They offer a useful demonstration of averted vision: you will find that when you direct your gaze to one, the other brightens and grows. This also shows that M10 has a much more distinct core.
6. Comet C/2017 K2 (PanSTARRS)
Recommend equipment: 15×70
Since its discovery five years ago, this comet has raised hopes of a good apparition as it approaches perihelion. During July, it is predicted to be within the grasp of small binoculars as it traverses Ophiuchus, passing M10 on the 15th. Although it brightens, it also moves southwards, so this could be the best time to observe it from UK latitudes.