Binocular tour

Curiosities include double-star Albireo, dark nebula Barnard’s E and enigmatic M71

1 The Dumbbell Nebula

We begin this month’s tour with the easiest planetary nebula for binoculars. Identify Gamma (a) Sagittae and pan a little over 3° in the direction of 15 Vulpeculae where, even in suburban skies, you will find a minuscule glowing cloud. This object, 1,360 lightyears distant, is the Dumbbell Nebula. Initially it will appear rectangular but with patience you should discern the slight narrowing in the middle that gives it its common name. ! SEEN IT

2 Albireo

Albireo (Beta (`) Cygni) marks the Swan’s eye. This double star has a separation of 34 arcseconds, a good test for 10x magnification. Once you have split it, notice the contrast between the golden mag. +3.1 primary and the azure mag. +5.0 secondary. Albireo was recently shown to be an optical double, ie, a line-of-sight coincidence. ! SEEN IT 3 The Ring Nebula

This month’s challenge is another planetary nebula. The mag. +9.5 Ring Nebula, M57, lies almost midway between Sheliak (Beta (`) Lyrae) and Sulafat (Gamma (a) Lyrae), which makes it easy to locate, but it's less easy to identify. At 15x, it is tiny and will appear as a defocused star; so don’t expect to see it as a ring. M57 is about 2,300 lightyears away, and has a diameter of 1 lightyear. ! SEEN IT

4 The Coathanger

We now head southeast to a popular star party piece, also known as Collinder 399, Brocci's Cluster and Al-Sufi's Cluster, which lies 8° south of Albireo.

It lies in a darker part of the Milky Way, so even small binoculars will reveal the 10 brightest stars that give this asterism (it is not a true cluster) its common name. It was first recorded by the Persian astronomer Abd al-Rahman al-Sufi in his AD 964 Book of Fixed Stars. ! SEEN IT

5 M71

After decades of dispute as to whether this object is a dense open cluster or a sparse globular cluster, the consensus is now that it is the latter. You’ll find it south of the mid-point of a line joining Delta (b) and Gamma (a) Sagittae. At mag. +8.2 it's quite faint, but 15x magnification should reveal that it is not a star, even with direct vision, and averted vision should confirm this. ! SEEN IT

6 Barnard’s E

One of the easiest dark nebulae you'll find is 1° west of Tarazed (Gamma (a) Aquilae). It’s a pair of nebulae, B142 and B143, and is easy to identify because of the rich starfield against which they lie. You’ll need a dark, transparent sky to catch these agglomerations of gas and dust. They appear either as an uppercase ‘E’ or an underlined ‘C’, depending on sky clarity. !

" Tick the box when you’ve seen each one