Mercury might be visible in northeastern morning twilight during the first days of August but closes rapidly with the Sun to be at superior conjunction on the 15th. It will not be observable at the evening apparition, setting too soon after the Sun. It will reappear in the morning sky in November. Venus is now deep in evening twilight and will be at inferior conjunction on the 18th when it passes south of the Sun. It will become prominent in the morning sky from September into 2008. Mars is in Taurus, brightening from 0.5 to 0.3 magnitude during the month. It rises in the northeast soon after 23h on the 1st and 22h by the 31st. Moon above on the 6th-7th. Mars below the Pleiades about the 20th.

Jupiter is a bright -2.3 magnitude in Ophiuchus, stationary on the 7th and setting about 22h by the 31st. Moon and Antares below on the 21st. Saturn is in conjunction with the Sun on the 21st and will not be observable this month. Uranus is in Aquarius rising soon after sunset in August. Moon nearby on the 2nd and 29th. Neptune is in Capricornus and at opposition on the 13th. Moon nearby on the 27th.

The Moon: last quarter 5d 21h, new Moon 12d 23h, first quarter 21d 00h, full Moon 28d 11h. The total eclipse of the Moon on the 28th will be visible from the Pacific Ocean region but not from Europe. Moon close below Antares on the 21st.

London area, sunset: 1 Aug 19h 50m 31 Aug 18h 50m, sunrise: 04h 20m, 05h 10m. Nautical twilight ends: 1 Aug 21h 30m, 31 Aug 20h 10m, begins: 02h 40m, 03h 50m. Edinburgh area, sunset: 1 Aug 20h 19m, 31 Aug 19h 09m, sunrise: 04h 15m, 05h 15m. Nautical twilight ends: 1 Aug 22h 22m, 31 Aug 20h 42m, begins: 02h 10m, 03h 45m.

The Perseids meteor shower reaches maximum activity during the night of the 12th-13th when, given a clear sky, some 60-80 meteors per hour can be expected. The Moon is new on the 12th, so conditions could be excellent. The radiant, from where the meteors appear to come, is shown on the chart between Perseus and Cassiopeia. The meteors can appear in any part of the sky but, if belonging to the Perseid stream, their paths trace back to this area. The real paths of the particles are essentially parallel when they enter the Earth’s atmosphere and the apparent divergence is an effect of perspective. Like most meteor showers, numbers build up over the days before maximum but drop off fairly rapidly afterwards. The Perseids and the December Geminids (also favourable this year) are the two most reliable annual showers. The Moon will spoil the major showers in 2008.

The Moon passes in front of the Pleiades star cluster every month in 2007 but not all events will be visible in a dark sky or from one location. Occultations of several stars in the Pleiades should be observable from NW Europe on 6-7 August (23-02h), 27-28 October (22-01h) and 21-22 December (21-00h). The Moon will be just past last quarter for the August event which will not begin until the rather late hour of midnight BST. The Moon does not follow the same path against the stars each month but swings north and south over an 18-year cycle, in which period two series of occultations occur each lasting about a year.

The glare from the Moon makes it difficult to see the Pleiades stars with the naked eye, so binoculars or a small telescope will make them easily visible and also show fainter stars. The stars will disappear at the illuminated eastern (left) limb or edge of the Moon and reappear at the darkened western or right-hand limb of the Moon. Four of the brighter stars will pass behind the Moon (in order), Celaeno (5.5), Electra (3.7), Taygeta (4.3) and Maia (3.9 magnitude), Celaeno and Electra close together at about 00h (1 am BST) but times vary by several minutes with your location.

The seven Pleiades which also include Alcyone, Merope and Sterope were the daughters of Atlas and Pleione who are also represented in the cluster. The Pleiades are commonly known as the Seven Sisters although only six stars are most easily seen. The whole cluster contains many more and in a dark sky a good, young eye may see a dozen or so. There has been much written about the missing Pleiad being Celaeno, the faintest of the seven, but there is no direct evidence that it has faded in historical time. This galactic or open cluster of stars, which would have formed as a group close together about 80 million years ago, is about 400 light years from us. The stars are hot and blue and involved in much nebulosity that shows on long-exposure photographs. The cluster of a hundred or more stars covers an area about twice the Moon’s diameter and is a splendid sight in binoculars or a wide-field telescope.

The diagram shows the brighter stars that will be above the horizon in the latitude of London at 23h (11pm) at the beginning, 22h (10pm) in the middle, and 21h (9pm) at the end of the month, local mean time. At places away from the Greenwich meridian the Greenwich times at which the diagram applies are later than the above by one hour for each 15 deg west of Greenwich and earlier by a like amount if the place be east. The map should be turned so that the horizon the observer is facing (shown by the words around the circle) is at the bottom, the zenith being at the centre. Greenwich Mean Time, known to astronomers as Universal Time and expressed in 24-hour notation, is used in the accompanying notes unless otherwise stated.