|Events during August
·The Perseids meteor shower can be seen at best from 11th to the 14th August.
·On the 28th there is a total eclipse of the Moon centred on the mid-Pacific.
·The Moon: Last quarter – 5th, New – 12th, First quarter – 21st, Full – 28th.
Augustīs snapshot shows the sky at 01.00h on the 13th, an ideal time for observing meteors from the Perseids meteor shower. This year there are very
favourable conditions for viewing the predicted average 60 meteors an hour as, with a new Moon on the 12th, they are free from lunar interference. You can see them
streaking out from the direction of the radiant point between the constellations of Perseus and Cassiopeia, shown on the snapshot. The best way to observe them is
to lie outdoors in a reclining chair or sun-lounger, facing north. At this time of year, if you have or can borrow a pool, you could try lolling on a lilo or,
if you prefer not actually getting wet, climb into a childīs paddling pool floating in the swimming pool – bliss with a glass of Cava. You can carry on watching,
as Perseus climbs higher in the sky, until dawn when sunlight will prevent observation. The hours preceding dawn are best to watch for meteors, when the speed of
the Earthīs rotation combines with that of its orbital motion, ploughing through the dust trail at maximum speed. Because meteor showers cover such a broad area
of the sky, they are best viewed with the naked eye as binoculars and telescopes restrict the field of vision.
The source of the Perseids shower is Comet Swift-Tuttle. Although nowhere near Earth, the comet's wide tail intersects Earth's orbit and we pass through it
every year in July and August. Sometimes called shooting stars, meteors can vary in size from a grain of sand, through pea-size producing a more spectacular display,
to rare stunning fireballs the size of an apple. Upon collision with Earthīs atmosphere, about 95 kilometres above Earthīs surface, they begin to glow white hot and
we witness a streak of light as they burn up. The shower is most intense from the 11th to the 14th August when Earth is in the dustiest part of the tail.
Note: Compare the snapshot at 01.00h on 13th August to the snapshot last month at the same time, 01.00h, on 16th July to see the difference in the apparent
location of the constellations.
||Mercury is at superior conjunction on the 15th and then moves into the evening sky too low for observation.
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 is very low in the evening sky until inferior conjunction on the 18th, after which she moves into the morning sky.
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 in Taurus rises about midnight by the end of August. The planet is below the Pleiades on the 8th and below the Moon on the 6/7th.
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 is in Ophiuchus at –2.2 magnitude, setting soon after midnight by the 31st. The planet is stationary on the 7th and above the Moon on the 21st.
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, in Leo, is in conjunction with the Sun on the 21st and not visible this month.
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, in Aquarius, rises at sunset by the 31st with the Moon nearby on the 28th.
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, in Capricorn, is at opposition on the 13th with the Moon nearby on the 26th.
Neptune has an average magnitude of 7.9 which varies little with changing distance.
||No longer an offical planet and never brighter than 13 magnitude, Pluto is only visible through powerful
telescopes and we therefore do not report on its position in the sky.
Last quarter: 5th
New moon: 12th
First quarter: 21st
Full moon: 28th
The Moon in 2007:
The Moon was seen unusually high and low in the sky during 2006 (see Moon). Although the extremities occurred last year, the Moon will still be seen very
high and very low each month this year, most noticeable around full Moon. It will be near full and high around the 2nd and 29th January, the 25th February
and the 24th March; and near full and low around the 1st and 28th June.
During each month of 2007, the Moon will pass through the Pleiades. This will mostly be in daylight but observable 01.00-04.00h 7th August,
0.00-03.00h 28th October and 22.00-01.00h on the 21st to 22nd December. Binoculars will give a clearer view.