Mercury
During the first week of August, Mercury remains visible low down towards the east-northeast just before sunrise. The planet is somewhat challenging to locate as it hovers only a few degrees above the horizon during morning twilight. On August 5th, the thin waning crescent Moon passes 4 degrees south of Mercury (mag. -0.6). The planet then passes through superior conjunction on August 24th and hence is unobservable for the remainder of the month.
Venus
During August, Venus is a spectacular "evening star" for observers located at southern latitudes and equatorial locations. By months end from the southern hemisphere the planet dazzles, setting just over 3 hours after the Sun. At magnitude -4.0, it's an unmistakable beacon above the western horizon.
Venus is also visible from northern temperate latitudes this month but remains inconveniently low down, setting just over 1 hour after the Sun. The phase of the planet decreases slightly as the month progresses, from 83% to 74% with its apparent size increasing from 13 to 15 arc seconds.
On August 10th, the 10% illuminated waxing crescent Moon passes 5 degrees south of Venus.
Mars
Mars is now a much easier morning object, rising 1.5 hours before the Sun from northern temperate latitudes and only slightly less from locations further south. The planet is currently moving direct and starts the month in Gemini before crossing the border into Cancer on August 24th. At magnitude +1.6, the famous "Red planet" is positioned just above the east-northeast horizon before dawn with the much brighter Jupiter located near by.
To the naked eye Mars appears red-orange in colour but with an apparent size of just 4 arc seconds, telescopically it's too small to spot any details.
On August 4th, the thin 6% illuminated waning crescent Moon passes 5 degrees south of Mars. Later on August 19th, Mars passes 6 degrees south of star Pollux, which at magnitude +1.1 is the brighter of the two objects.
Jupiter
Jupiter is a beautiful early morning object moving direct amongst the stars of Gemini. The visibility, magnitude and apparent size of this giant planet continues to improve slightly this month. It brightens from magnitude -1.9 to -2.0 and the apparent size increases from 33 to 35 arc seconds as August progresses.
Located above the east-northeast horizon, Jupiter rises over 2 hours before the Sun at months end. Through binoculars spotting the 4 Galilean moons of Jupiter should be possible despite the low altitude.
The waning 6% illuminated waning crescent Moon passes 4 degrees south of Jupiter on August 3rd and again on August 31st. Also located nearby during the first of these two conjunctions is Mars, with the three objects forming a nice grouping.
Saturn
Saturn remains visible as an evening object throughout August but its period of visibility continues to decrease as it draws towards the Sun. The ringed planet and be spotted as soon as its dark enough towards the west-southwestern sky amongst the stars of Virgo.
By the end of the month, Saturn sets only 2 hours after the Sun from northern temperate latitudes. Observers located in the tropics and further south have it much better, with the planet setting up to more than 4 hours after the Sun.
Saturn in Virgo during August 2013 - pdf format
Saturn's magnitude decreases from +0.6 to +0.7 and its apparent size from 17 to 16 arc seconds during August.
On August 13th, the 38% illuminated Moon passes 3 degrees south of Saturn.
Uranus
Uranus, magnitude +5.8, is now a late evening object amongst the stars of Pisces. At the start of the month, the distant planet rises in the east before midnight and continues to rises a little earlier each day as the month progresses. It then remains visible for the remainder of the night.
From a dark site the planet is just about a naked eye object, but if you can't spot it, use binoculars or a small telescope to easily notice it. On August 24th, the 87% illuminated waning gibbous Moon passes 3 degrees north of Uranus.
Uranus Finder Chart for August 2013 - pdf format
Neptune
Neptune (mag. +7.8), the most distant planet in the solar system reaches opposition in Aquarius on August 27th and hence is visible all night long. At opposition the planet is positioned 28.973 AU (4334 million km or 2693 million miles) from Earth.
With a declination of -10 degrees, Neptune is currently situated better for observation for observers located in either the tropics or southern hemisphere than for those in the northern hemisphere.
Neptune Finder Chart for August 2013 - pdf format
Neptune is positioned just over 1 degree to the west of Sigma (σ) Aquarii mag. +4.8. The planet is too faint to be seen with the naked eye but is visible with binoculars. A small to medium sized telescope at high magnifications will show the planet as a small bluish disk, although the surface will appear devoid of details.
On August 21st, the full Moon passes 6 degrees north of Neptune.
Solar System Data Table August 2013
| Date | Right Ascension | Declination | Apparent Magnitude | Apparent Size | Illum. (%) | Distance from Earth (AU) | Constellation | |
|---|---|---|---|---|---|---|---|---|
| Sun | 5th Aug 2013 | 09h 00m 06.3s | 17d 02m 06.1s | -26.7 | 31.5' | 100 | 1.014 | Cancer |
| Sun | 15th Aug 2013 | 09h 38m 04.4s | 14d 07m 27.6s | -26.7 | 31.6' | 100 | 1.013 | Leo |
| Sun | 25th Aug 2013 | 10h 15m 08.2s | 10d 50m 29.3s | -26.7 | 31.6' | 100 | 1.011 | Leo |
| Mercury | 5th Aug 2013 | 07h 44m 31.0s | 20d 43m 07.9s | -0.6 | 06.6" | 59 | 1.019 | Gemini |
| Mercury | 15th Aug 2013 | 08h 58m 42.5s | 18d 28m 28.8s | -1.4 | 05.4" | 90 | 1.247 | Cancer |
| Mercury | 25th Aug 2013 | 10h 18m 11.5s | 12d 25m 57.4s | -2.0 | 04.9" | 100 | 1.361 | Leo |
| Venus | 5th Aug 2013 | 11h 10m 10.4s | 06d 39m 18.9s | -3.9 | 12.8" | 82 | 1.306 | Leo |
| Venus | 15th Aug 2013 | 11h 53m 24.7s | 01d 35m 41.2s | -4.0 | 13.4" | 79 | 1.241 | Virgo |
| Venus | 25th Aug 2013 | 12h 35m 59.9s | -03d 33m 24.5s | -4.0 | 14.2" | 76 | 1.173 | Virgo |
| Mars | 5th Aug 2013 | 07h 04m 38.9s | 23d 21m 06.1s | 1.6 | 03.9" | 98 | 2.388 | Gemini |
| Mars | 15th Aug 2013 | 07h 32m 54.5s | 22d 34m 09.8s | 1.6 | 04.0" | 97 | 2.357 | Gemini |
| Mars | 25th Aug 2013 | 08h 00m 27.1s | 21d 30m 28.3s | 1.6 | 04.0" | 97 | 2.321 | Cancer |
| Jupiter | 5th Aug 2013 | 06h 37m 31.8s | 22d 59m 51.0s | -1.9 | 33.1" | 100 | 5.948 | Gemini |
| Jupiter | 15th Aug 2013 | 06h 46m 17.9s | 22d 51m 55.3s | -2.0 | 33.7" | 100 | 5.856 | Gemini |
| Jupiter | 25th Aug 2013 | 06h 54m 32.1s | 22d 42m 51.8s | -2.0 | 34.3" | 99 | 5.748 | Gemini |
| Saturn | 5th Aug 2013 | 14h 15m 02.6s | -11d 03m 08.9s | 0.6 | 16.7" | 100 | 9.924 | Virgo |
| Saturn | 15th Aug 2013 | 14h 16m 58.6s | -11d 15m 43.5s | 0.7 | 16.5" | 100 | 10.086 | Virgo |
| Saturn | 25th Aug 2013 | 14h 19m 26.9s | -11d 30m 47.3s | 0.7 | 16.2" | 100 | 10.241 | Virgo |
| Uranus | 5th Aug 2013 | 00h 45m 58.3s | 04d 09m 39.7s | 5.8 | 03.6" | 100 | 19.512 | Pisces |
| Uranus | 15th Aug 2013 | 00h 45m 18.4s | 04d 05m 10.4s | 5.8 | 03.6" | 100 | 19.376 | Pisces |
| Uranus | 25th Aug 2013 | 00h 44m 23.6s | 03d 59m 08.1s | 5.8 | 03.7" | 100 | 19.258 | Pisces |
| Neptune | 5th Aug 2013 | 22h 25m 54.6s | -10d 32m 51.1s | 7.8 | 02.4" | 100 | 29.040 | Aquarius |
| Neptune | 15th Aug 2013 | 22h 24m 55.9s | -10d 38m 40.8s | 7.8 | 02.4" | 100 | 28.992 | Aquarius |
| Neptune | 25th Aug 2013 | 22h 23m 54.4s | -10d 44m 43.5s | 7.8 | 02.4" | 100 | 28.973 | Aquarius |