Our celestial neighbourhood in August
PICK OF THE MONTH
Saturn
Best time to see: 14 August, 00:00 UT
Altitude: 22º (low)
Location: Capricornus
Direction: South
Features: Rings, banded atmosphere, weather systems
Recommended equipment: 75mm or larger
Saturn reaches opposition on 14 August, a time so-named because the planet is in the opposite part of the sky to the Sun. A view of Saturn in the week running up to opposition will show the rings getting brighter. In the week after opposition, the rings slowly appear to revert back to their normal brightness.
This is due to what’s known as the opposition effect, a phenomenon caused by the shadows of the ring particles being reduced to a minimum as seen from Earth at opposition.
As has been the case for several years now, it’s Saturn’s north pole which is angled towards us. The tilt angle is slowly decreasing year on year, with minor variations within each year. Through August it changes from +13.3 to +14.3, which is low enough to keep the northsouth extremes of the rings well within the boundaries of the planet’s globe. At present they extend to a point roughly half-way between the apparent centre and poles of the planet.
At opposition Saturn manages a peak brightness of mag. +0.3 and is above the horizon from when the sky begins to darken the onset of dawn. The full Moon sits near to Saturn on the nights of 11/12 and 12/13 August.
Saturn’s declination is slowly increasing which means it’s getting higher in UK skies. This is a good thing as far as viewing the planet goes, as Saturn will appear less affected by low-level atmospheric turbulence. Through a telescope, the rings are the most obvious feature, but attention should be made to look for variations on the disc as well. As well as subtle banding, bright patches representing storms may sometimes be seen as well.
Mercury
Best time to see: 1 August, 30 minutes after sunset
Altitude: 2º (extremely low)
Location: Leo
Direction: West-northwest On 1 August, Mercury shines at mag. –0.5 but sets just 40 minutes after the Sun. At greatest eastern elongation on 27 August, despite an impressive 27.3º separation from the Sun, the mag. +0.3 planet sets 30 minutes after sunset and is unlikely to be seen.
Venus
Best time to see: 1 August, 30 minutes before sunrise
Altitude: 11º
Location: Gemini
Direction: East-northeast On 1 August, Venus rises 120 minutes before the Sun and shines at mag. –3.8. By 31 August it rises 90 minutes ahead of the Sun. Through a telescope, Venus appears as an almost full circle at the end of the month, 97%-lit and 10 arcseconds across. A slender 4%-lit waning crescent Moon lies 9º above Venus, as seen from the UK, on the morning of 25 August and as a very thin 1%-lit waning crescent 4.3º from Venus on the morning of 26 August.
Mars
Best time to see: 31 August, 04:00 UT
Altitude: 51º
Location: Taurus
Direction: Southeast Mars starts the month at mag. +0.2, 1.3º to the south of mag. +5.8 Uranus, then passes 5.9º south of the Pleiades open cluster on the morning of 18 August. The last quarter Moon sits near to the planet on the morning of 19 August. Mars reaches the mag. 0.0 threshold on 21 August. Through a telescope, the planet increases in apparent size from eight arcseconds on 1 August to nine arcseconds on 31 August.
Jupiter
Best time to see: 31 August, 02:00 UT
Altitude: 38º
Location: Cetus
Direction: South Jupiter is improving as it approaches opposition next month. By mid-August it reaches its highest point in the sky, due south in darkness. On 15 August, mag. –2.6 Jupiter is joined by an 87%-lit waning gibbous Moon. By the end of August, the planet brightens to mag. –2.7 in Cetus, right on the border with Pisces.
Uranus
Best time to see: 31 August, 03:00 UT
Altitude: 49º
Location: Aries
Direction: South-southeast On the morning of 2 August, mag. +0.2 Mars is located 1.3º south of mag. +5.8 Uranus. By the end of August, now at mag. +5.7, Uranus is able to reach an altitude of 50º under truly dark skies.
Neptune
Best time to see: 31 August, 01:15 UT
Altitude: 34º
Location: Aquarius
Direction: South Neptune slips across the border from Pisces into Aquarius on 18 August. At mag. +7.8, the planet is technically visible to the naked eye, but can be challenging. Reaching opposition next month, Neptune is very well placed for UK observation.
The planets in August
The phase and relative sizes of the planets this month. Each planet is shown with south at the top, to show its orientation through a telescope
Jupiter’s moons: August
Using a small scope you can spot Jupiter’s biggest moons. Their positions change dramatically over the month, as shown on the diagram. The line by each date represents 01:00 BST (00:00 UT.)
