Date (2010)	Times of first sighting and setting of the crescent Moon*
	London	Manchester	Leeds	Glasgow
11 Aug	Crescent moon visible with binoculars around 20:36; sets 20:42	Crescent moon visible only with binoculars, around 20:48; sets 20:51	Crescent moon visible only with binoculars, around 20:46; sets 20:49	Crescent moon not visible with telescope
12 Aug	Crescent moon easily visible around 20:43; sets 21:01	Crescent moon easily visible around 20:55; sets 21:08	Crescent moon easily visible around 20:52; sets 21:05	Crescent moon easily visible around 21:06; sets 21:14
9 Sept	Crescent moon not visible	Crescent moon not visible	Crescent moon not visible	Crescent moon not visible
10 Sept	Crescent moon easily visible around 19:35; sets 19:45	Crescent moon easily visible around 19:42; sets 19:48	Crescent moon easily visible around 19:39; sets 19:44	Crescent moon easily visible around 19:49; sets 19:49

*Times are BST not GMT, and may not correspond exactly with the official (religious) sighting of the crescent moon.

The dates of Ramadan and other Islamic months depend on the sighting of the new crescent Moon.

Information on the visibility of the Moon from anywhere in the world is available from HM Nautical Almanac Office's Websurf facilty:

• accept the conditions of use (Websurf homepage)
• select the 'Moon-Viz' link
• choose or search for a place
• select a date range
• The visibility information (time) is in the 'BEST TIME' column; Moon set time is in the 'Moon set' column. NB add +1 hour for BST.

For the last few weeks, H2 has been in the horology conservation workshop at the Royal Observatory undergoing research. The work, which is part of the continuing research for a full published catalogue of the NMM's collection of marine chronometers, involves the complete dismantling of the timekeeper. Every part is being studied, measured and photographed, the intention being to take a fresh look at Harrison's work on his longitude machines.

Last year H1 was dismantled and studied, and some interesting comparisons can now be made about Harrison's early work. It has always been believed that the simple portrayal of Harrison as a lone craftsman, was too simplistic, and we know that H1 was constructed with the help of Harrison's brother James, and almost certainly with advice and supplies from George Graham's contacts in London.

Harrison is known to have had help in his construction of H2, which was made in London, and the current study confirms this, with a much more professional feel to the materials and the finishing of this timekeeper; if H1 is a reminiscent of a fascinating 'country clock', then H2 has all the trappings of a 'scientific instrument'.

There is no doubt Harrison had help in construction, but this doesn't diminish the status of this extraordinary timekeeper, which teems with interesting 'Harrisonian' designs and construction features.

The timekeeper is now completely dismantled and before reassembly can begin there is full photography and measurement for CAD drawings to be done. Analysis is also planned on both the special alloys and the wood used in the timekeeper. It has always been said that the latter is lignum vitae, but as far as is known this has never been positively proved before.

Further updates will follow before the timekeeper returns to exhibition in the Longitude Gallery, now estimated to be sometime in late July.

The summer solstice occurs today, 21 June, at 11.38 UTC (GMT).

The summer and winter solstices mark the times when the Sun is at its furthest from the celestial equator (the projection of the Earth's equator onto the sky). The world 'solstice' comes from the Latin solstitium meaning 'Sun stands still' because the apparent movement of the Sun's path north or south stops before changing direction.

The summer solstice does not always fall on 21 June. Because the Earth takes approximately 365.25 days to go around the Sun, the precise time of the solstices and equinoxes occurs about 6 hours (0.25 days) later each year, with a jump of a day backwards on leap years. The last time the summer solstice was not on 21 June was 1975 when it occurred on 22 June at 00.27, and in the year 2012 it will occur on 20 June at 23.09.

Find out more about solstices and equinoxes in our fact file.

Hour Angle

To mark the solstice, the Royal Observatory is hosting Hour Angle by composer John Eacott, a free musical performance sonifying the exact moment of the summer solstice. A real-time calculation of the Sun's declination will be transformed into live notation played by 12 musicians. The piece will allow visitors the chance to experience the solstice in an unforgettable way. The performance will start promptly at 12.08. Visitors are advised to arrive early.

Karen Gillan (Doctor Who's Amy Pond) visits the Royal Observatory, Greenwich to learn about the Prime Meridian Line with space scientist Dr Maggie Aderin-Pocock, and the Great Bear with public astronomer Dr Marek Kukula.

Clip from Doctor Who Confidential, Series 5 Episode 11: Extra Time. First broadcast on BBC Three, 7:30pm Saturday 12 June 2010. Used by permission.

www.bbc.co.uk/doctorwho/s4/confidential/

Part public lecture, part planetarium show, the Royal Observatory has joined forces with research scientists in three of the most exciting fields of modern space science to bring you a new experience in astronomy talks. With a mixture of stunning telescope images and full-dome visuals our trio of experts will show you the Universe and the science behind it as you've never seen it before. All of our guest speakers are accomplished science communicators and their talks are suitable for a general audience.

Astrobiology: the new science of life in the Universe

Dr Lewis Dartnell (University College London)

Thurs 17 June, 19.00
Cost: £8/£6

Astrobiology is a brand new field of science, bringing together biologists, astronomers and planetary scientists to investigate the origins and limits of life on our planet and discover where life might exist beyond the Earth. Join Dr Lewis Dartnell on a tour of the planets and moons of our Solar System - and further afield to alien worlds orbiting distant stars - to explore one of the greatest questions ever asked: are we alone?

Violent birth: a Universe of star formation

Dr Mark Westmoquette (University College London)

Weds 14 June, 19.00
Cost: £8/£6

The birth of new generations of stars has shaped the evolution of our Universe for billions of years. Starbursts are one of the most extreme examples of this process: entire galaxies convulsed by a frenzy of new star formation that can blast clouds of gas thousands of light years into intergalactic space. Dr Mark Westmoquette guides us through these violent cosmic neighbourhoods and explains how such colossal star factories can help us to unravel the complex history of the Universe.

Our place in the Universe

Dr Rita Tojeiro (University of Portsmouth).

Thurs 19 August, 19.00
Cost: £8/£6

Over the last few decades astronomers have made enormous leaps in charting the Universe around us. Now, with accurate positions for millions of galaxies, we are finally able to trace the Cosmic Web in which we live. But these cosmic maps do far more than simply catalogue the contents of our Universe - they can help us to understand its origin and evolution as well as its ultimate fate. Cosmologist Dr Rita Tojeiro takes us on a voyage to the furthest reaches of space and explains how astronomers are unlocking some of the fundamental secrets of the Universe.