Date (2011)	Times of first sighting and setting of the crescent Moon*
	London	Manchester	Leeds	Glasgow
31 July	Crescent moon not visible	Crescent moon not visible	Crescent moon not visible	Crescent moon not visible
1 Aug	Crescent moon visible under perfect conditions around 20:58; sets 21:09	Crescent moon visible under perfect conditions around 21:12; sets 21:19	Crescent moon visible under perfect conditions around 21:10; sets 21:16	Crescent moon easily visible around 21:27; sets 21:29
30 Aug	Crescent moon not visible with a telescope	Crescent moon not visible	Crescent moon not visible	Crescent moon not visible
31 Aug	Crescent moon easily visible around 20:03  sets 20:18	Crescent moon easily visible around 20:11; sets 20:23	Crescent moon easily visible around 20:09; sets 20:19	Crescent moon easily visible around 20:19; sets 20:25

*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.
   

Also of interest

• - Al Hijra and the Islamic Calendar – fact file
• - Persian astrolabe – a beautiful astrolabe dating from 1070AH by the Islamic calendar, and including a grid for finding the direction of Mecca from a number of different towns and cities.
• - Arabic (Islamic) brass globe – 18th-century globe showing all 48 constellations that were known to the Ancient Greeks, and engraved with the Arabic names of some of the stars.
• - Transmission of knowledge – as Islam spread across Northern Africa from the 7th century, it helped change the purpose of astronomy: for example, it was now needed to produce accurate tables of prayer times.
   

If you’re up at the Observatory in the next few months, see if you can find a collection of meteoritic mirrors scattered throughout the Astronomy galleries. There are six mirrors on display next to objects and instruments that have played a key role in our study of the Universe. They’re beautiful, enigmatic objects and there’s no explanation or text in the galleries to tell you why they’re there. It’s up to you to investigate and come to your own conclusions…

Artist and blacksmith Matthew Luck Galpin’s ‘Anvilled Stars‘ are meteorites that have been heated, hammered, ground and polished into mirrored works of art. The meteorites used to create ‘Anvilled Stars’ are thought to be more than 4.5 billion years old, and they started out as part of the asteroid belt during the early life of the Solar System. They reached Earth between 4000-6000 years ago after a journey lasting millions of years; they shattered as they entered the atmosphere and crashed into the northern Argentinian desert, witnessed by the local people. The place where they landed is now called Campo del Cielo – the Field of Heaven.

Meteorites are pieces of rock and metal that have fallen from space, providing some of the only physical evidence we have to study the formation of the Solar System. Mirrors are significant not only because they reflect us and our world, but also as the essential components of instruments such as telescopes that we use to study the Universe. By bringing the two together Matthew’s work is a creative response in relation to the Universe and our place in it. Matthew says of the artwork: “by working these iron meteorites and mirroring their trajectory, I feel closer to belonging to their journey through space and time, reaching a point of reflection of our part in it all”.

Each mirror is unique, and their irregular shapes and cloudy impurities are a joint product of their ancient origins and their transformation into manufactured objects in Matthew’s workshop. The six mirrors form an imaginary ‘constellation’ across the Observatory site and it’s up to visitors to locate them all. Five more of Matthew’s mirrors are currently on display at the Science Museum in South Kensington, forming a larger constellation of eleven Anvilled Stars spanning London – just the latest chapter in their continuing 4.5-billion year story.

Impact: Collisions & Catastrophes

The Impact exhibition (open at the Royal Observatory until 29 August) takes a look at the fiery debris that bombards earth from space, sometimes laying waste to vast areas and even triggering mass extinctions of plants and animals. It also explores the vital clues that asteroids and meteorites provide about the violent formation of the Solar System.

The Royal Observatory, Greenwich is famously the home of the Prime Meridian of the World (0° Longitude) where each day and year officially begins, and of Greenwich Mean Time (GMT), as well as of the celebrated Harrison timekeepers.

Now the Royal Observatory is also home to OMEGA‘s London 2012 Countdown Clock. Installed on the Prime Meridian Line by OMEGA, the Official Timekeeper of the Games, the clock will tick away the seconds, minutes, hours and days until the start of the London 2012 Olympic Games – some of which will be hosted in Greenwich Park.

The clock was unveiled yesterday (27 July 2011) in time to celebrate ‘One Year to Go’ to the start of the Games.