|Events during August
The Moon: First quarter – 2nd and 31st, Full moon – 9th, Last quarter – 16th, New moon – 23rd. Mercury is at greatest elongation on the
7th and Saturn is in conjunction with the Sun on the same day, Neptune is at opposition on the 11th and the Perseids Meteor shower is from the 11th to 14th
August (conditions unfavourable with a full Moon just before on the 9th). From 9th to 27th August Mercury, Venus and Saturn will be in close proximity in
the northeast dawn sky from 6.30h and the crescent Moon will join them on the 21-22nd.
||Mercury, at 0.0 magnitude, is at greatest western elongation (19º) on the 7th August. The planet brightens
to –1.0 magnitude by the 15th and is visible in the northeast morning twilight in mid-month. Mercury is close below Venus on the 9th and near Saturn on
The best times to observe Mercury are when it is an evening star in the spring and a morning star in the autumn. In midsummer the lighter skies make visibility difficult near the horizon.
||Venus has been a bright –3.9 magnitude object since June and continues at this brilliance through August and
September. Venus rises 2 hours before the Sun at the beginning of August and falls into morning twilight by the end of the month. The Moon is closeby on the
On the 8th June 2004, Venus was at inferior conjunction
and transited the Sun. Transits of Venus are rare, taking place at greater
than 100 year intervals and usually in pairs. The last two transits of Venus were in 1874 and 1882. June's transit
began at 7.20h and lasted 6 hours until 13.20h, the total event visible from Europe as a small black disc crossing
the lower part of the sun from left to right. The next transit will be in late June 2012. After that, transits of Venus
won't occur again until 2117 and 2125.
Before and after inferior conjuction, when Venus is
the closest it comes to the earth, are the times at which the planet is most brilliant and can be seen setting or rising
4 hours after or before the sun. The dates of the next two inferior conjunctions are October 28th 2010 and October 26th 2018.
||Mars sets only minutes after the Sun and will not be visible again until pulling away from the Sun in
At opposition on the 28th August 2003, Mars was only 56 million kilometres from the earth. It showed a
disc of 25.1 seconds of arc across which is almost as large as it can ever appear. Mars started 2003 at 310 million kilometres from
the earth at 4.5 seconds of arc and 1.6 magnitude. By opposition it brightened 50 times to reach -2.9 magnitude but faded to 0
magnitude by December. Even to the naked eye Mars was a striking object in the summer and autumn sky, easily identifiable by its
reddish hue in an area of sky poor in bright stars. Mars will not be as close again for another 15 years.
These favourable oppositions occur every 15 years but other oppositions occur at average intervals of 2 years 2 months. In general Mars is observable every other year, being too close to the sun for favourable conditions during other times. Brightness at opposition varies from -1.0 to -2.9 magnitude, and when furthest from the earth it fades to 1.7 magnitude. The planet can be identified by its orange-red colour.
||Jupiter fades a little further to –2.0 magnitude and remains in Libra. The planet sets before 23.00h by the
end of August. The Moon is closeby on the 1-2nd and again on the 29th.
Being 770 million kilometres from the sun, the difference in brightness between opposition and conjunction varies less than with Mars, from about -2.8 to -1.8 magnitude.
The 4 largest moons of Jupiter are easily visible through a small telescope, ranging from 4.6 to 5.6 in magnitude. The innermost, Io, takes 1.8 days to orbit the planet making its motion easily detectable within a few minutes.
||Saturn is in conjunction with the Sun on the 7th August but by the end of the month is visible close to Venus
on the 26-28th.
Saturn crossed the equator into the northern hemisphere in 1996 where it will remain until 2010 with the southern side of the ring system facing the earth. Because of its distance, its brightness varies little between opposition and conjunction but is affected by the huge ring system. Seen edge on the rings contribute little or no light.
Every 15 years the plane of Saturn's rings passes through the sun, illuminating first the north and then the south side. For a few days the rings are edge on to the sun. About the same time the earth passes through the ring plane and, depending on the earth's position this may happen just once or 3 times. During 1995/96 there was a triple crossing and the next will be 2038/39. The next single crossings will be in 2009 and 2025.
Saturn's largest moon, Titan, is visible in small telescopes orbiting outside of the ring system.
||Uranus remains in Aquarius and rises about sunset by the end of August. The Moon is closeby on the 10th.
Brightness varies slightly reaching 5.6 magnitude at opposition. This is bright enough to see with the naked eye but identifying it against the stars is difficult.
||Neptune, remaining in Capricorn, is at opposition to the Sun on the 11th and due south at 2.00h. The Moon is
closeby on the 9th.
Neptune has an average magnitude of 7.9 which varies little with changing distance.
||Never brighter than 13 magnitude, Pluto is only visible through powerful telescopes and we will therefore not be reporting on its position in the sky.|
||First quarter: 2nd and 31st
Full moon: 9th
Last quarter: 16th
New moon: 23rd