For what seems to have been a long time, Saturn has been appearing very low in UK skies. The reason for this was because it was moving along the most southerly part of the ecliptic.
Passing through the constellations of Ophiuchus, the Serpent-bearer and Sagittarius, the Archer, Saturn has been low down and difficult to view.
During 2021, things are slowly beginning to improve. Now in Capricornus, the Sea Goat, it is able to reach a peak altitude of 19˚ as seen from the centre of the UK: not brilliant but definitely an improvement over the 14˚ peak altitude of 2018!
The planet reaches opposition on 2 August and during June 2021 is almost able to reach its peak altitude in what passes for a dark sky at this time of year.
On 27 June a bright 92%-lit waning gibbous Moon sits southwest of the planet in the dawn twilight.
On 28 June, now showing an 85%-lit waning gibbous phase, the Moon sits over to the east-southeast and forms a squat, down-pointing triangle with Jupiter and Saturn.
Low altitude isn’t ideal for getting a decent telescopic view of a planet. Low down, you are looking through a thicker layer of atmosphere.
Unsteady at the best of times, a thicker layer just increases the amount of wobbly air you need to look through.
If you are lucky enough to get a steady view, Saturn’s rings are currently nicely on view. Saturn’s northern pole is currently tipped towards Earth by 17˚.
Telescopically, look out for the shadow of the planet’s globe on the rings – currently easiest to see to the west of the globe.
Also look out for the razor thin dark ‘gap’ between the bright A and B rings. This is the Cassini Division, its visibility being a good indicator of steady conditions.
How to see the planets in June 2021
Best time to see: 30 June, from 02:45 BST (01:45 UT)
Features: Rings, banded atmosphere, occasional storms, brightest moons
Recommended equipment: 75mm or larger
Best time to see: 30 June, 40 minutes before sunrise
Altitude: 1˚ (extremely low)
This month we find Mercury in the evening sky, heading back towards the Sun for inferior conjunction, which occurs on 11 June. This follows an excellent period of evening visibility for this tricky planet last month. On 1 June, Mercury sets one hour after the Sun, but is dim at mag. +3.2. This will make it hard to spot against the bright evening twilight.
After inferior conjunction on 11 June, it returns to the morning sky but is poorly positioned. On 30 June, at mag. +1.1, the planet rises approximately an hour before the Sun, but visibility is compromised by low altitude.
Best time to see: 30 June, from 30 minutes after sunset
Altitude: 7˚ (low)
Venus is an evening planet, setting 1.5 hours after the Sun on 1 June, a time that doesn’t vary much over the month. The Moon lies nearby on 11 June as a thin 1%-lit waxing crescent and on 12 June as a 5%-lit waxing crescent. The biggest issue with viewing the planet is low altitude after sunset.
Best time to see: 1 June, from 22:45 BST (21:45 UT)
Mars is now too small for serious telescopic observation, the planet appearing just 3.9 arcseconds across at the end of the month. Mars cannot be seen against a dark sky this month and at mag. +1.8 will be tricky to spot against a bright June evening twilight. An 11%-lit waxing crescent Moon passes 2˚ north of Mars on 13 June.
Best time to see: 30 June, from 04:00 BST (03:00 UT)
Jupiter rises three hours before the Sun at June’s start, attaining a maximum height of 20˚ above the south-southeast horizon as the Sun rises. A 62%-lit waning gibbous Moon sits southwest of Jupiter on the morning of 1 June and, with a 76%-lit waning gibbous phase, to the southeast of the planet on 29 June. Jupiter rises five hours before the Sun by the month’s end when it’s possible to observe it close to maximum altitude as it nears its most southerly position in the sky.
Jupiter’s equinox was on 2 May, a time when the planet is sideways on to the Sun. For the next few months its four largest moons, the so-called Galilean moons, can appear to interact in mutual events, and Callisto casts its shadow on Jupiter. As Jupiter is now pulling away from the Sun in the morning sky, it’s easier to see some of the better-timed events.
A Jovian equinox basically flattens the moon’s orbital ellipses into an almost straight line. The three inner moons regularly cross Jupiter’s disc, but this is not the case for outer Callisto except when near to a Jovian equinox.
Not visible this month.
Not visible this month.
Pete Lawrence is an experienced astronomer and a co-host of The Sky at Night. The