WHEN: All month, but best conditions will likely be in the second half of June, when the Moon is out of the way The first half of 2017 has been good for binocular comets and we’ve been following several over recent months. During June and July there’s a final opportunity to catch comet C/2015 V2 Johnson from the UK, before it disappears below the horizon. This comet is predicted to be brightest during the first week of June when it should reach mag. +6.7. By the end of the month it will have dimmed only slightly to mag. +7.0 which still keeps it within binocular range. The Moon won’t help matters during the first half of June, but after the 13th it should be possible to dodge any serious interference.
At the start of June it is approximately 5º south of mag. +2.5 Izar (Epsilon (¡) Boötis), after which it passes south to sit roughly 4º east of mag. +0.2 Arcturus (Alpha (_) Boötis) on 5 and 6 June. It appears a little over 2º west of mag. +4.5
Zeta Boötis at 01:00 BST (00:00 UT) on 9 June. Centre Zeta in a pair of binoculars and the comet should appear as a smudge at the 3 o’clock position.
On 15 June, C2015 V2 Johnson slips over the border into Virgo. It crosses
the imaginary line between the stars 109 Virginis and Tau (o) Virginis (mag. +3.7 and mag. +4.2) on the night of 19 June. Continuing south, its journey takes it 0.5º west of mag. +4.1 Iota (f) Virginis at 12:00 BST (11:00 UT) on 27 June. From the UK it appears 0.66º northwest of Iota at 01:00 BST (00:00 UT) on 27 June, and 1º southwest of it at the same time on 28 June.
The comet continues its southerly plunge throughout July and will probably be lost from view in the UK from the third week of July onwards. On the night of the 1st it passes extremely close to mag. +4.2 Kappa (g) Virginis. Closest approach is around 22:30 BST (21:30 UT) when the comet will be approximately 1 arcminute to the east of this star.
Comet 71P/Clark will present more of a challenge, but its proximity to mag. +1.0 Antares (Alpha (_) Scorpii) should help. At mag. +11.8, the comet is a telescope object and is slightly less than 2º east-southeast of bright Antares at 01:00 BST (00:00 UT) on 1 June. At 01:00 BST (00:00 UT) on 4 June it passes between Antares and mag. +2.8 Tau
(o) Scorpii, crossing the imaginary line joining them, four-fifths of the way along from Antares.
C/2015 V2 Johnson passes from Boötes through Virgo as it vanishes from UK horizons
Comet 71P/Clark is close to Antares in early June; the bright star should help you find it