The August night sky

Starwatch August 1
Starwatch Photograph: Guardian

The Summer Triangle of Deneb, Vega and Altair looms high on the meridian at our star map times as Jupiter stands low in the E having risen 30 minutes earlier. The giant planet, the target for Nasa’s Juno mission whose launch window opens on Friday, dominates the sky for the rest of the night and climbs high into the SE to S by dawn.

This month Jupiter brightens from mag -2.4 to -2.6 as its distance falls and it swells to 45 arcsec in diameter. Small telescopes show its cloud bands while binoculars are all we need to glimpse its four main moons. Catch Jupiter near the Moon on the 20th and 21st.

Saturn, mag 0.9 and 12° to the right of Spica in Virgo, is sinking in our W evening twilight and may be lost from Britain by mid-month, though observers farther S may follow it for another month or more. Look for it very low down and almost directly below Arcturus, the most conspicuous star in the W at nightfall.

Mars, reddish in hue and mag 1.4, rises in the NE by 02:00 BST and stands higher towards the E by dawn. August sees it track into Gemini where it passes the star cluster M35 on the 6th and 7th, stands to the left of the waning Moon on the 25th and lies 8° to the right of Pollux by the 31st. Less than 5 arcsec wide, it is too small to excite telescopic interest.

Venus rounds the Sun‘s far side on the 16 and is not observable. Binoculars may show Mercury very low in the ENE twilight as the month ends as it begins a favourable spell as a morning star.

The Perseids meteor shower lasts until the 24th but peaks in bright moonlight on the 13th so only its brightest meteors might be seen as they diverge from the Perseids radiant (see N map). Meteor counts should increase as this point climbs through the NE and E towards the zenith by dawn.

August diary

4th 113h Moon 8° S of Saturn.

6th 12h First quarter.

13th 05h Peak of Perseids meteor shower; 20h Full moon.

16th 13h Venus in superior conjunction.

17th 02h Mercury in inferior conjunction.

20th 13h Moon 5° N of Jupiter.

21st 23h Last quarter.

23rd 00h Neptune at opposition.

25th 15h Moon 2.7° S of Mars.

28th 02h Moon 2.6° S of Mercury.

29th 04h New moon.

30th 19h Jupiter stationary.

* Times are BST.

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