Photo C7817 © National Maritime Museum

Once the clocks go back, at the end of October, we'll start opening the 28-inch telescope for evening viewings.

Jason Lewis completed his human-powered circumnavigation at the Royal Observatory, just after 12.30pm today. He and his supporters heaved Moksha, his wooden pedal boat, across the Prime Meridian to mark the occasion.

There are already pictures of the event on Flickr, which we've saved as our favourites. Tag your own pictures with the expedition's preferred tag 'expedition360' so we can find and share them.

New dates are available for our evening observing events.

Astronomers will be running a workshop about using telescopes at the Observatory on the evening of 19th January from 5pm – 8pm. Perhaps you've received a new telescope for Christmas and would like some advice on getting the most from it, or you're considering buying a telescope but are unsure what to look for? This workshop will let you discuss the different telescopes available on the market, try out different models and find out what they can do. Tickets cost £15 (£11 concessions) and can be booked in advance via bookings@nmm.ac.uk.

The Royal Observatory has a new program of spring courses for the general public. You can learn how to take photographs of the night sky at our astrophotography workshop, or learn about the Big Bang and black holes at one of our monthly lectures.

Download the full programme of courses and talks as a PDF leaflet.

On Friday the 1st of August, there will be a total eclipse of the Sun. The total eclipse will be visible from a narrow path crossing the Earth, starting in Northern Canada, passing over Greenland & the Arctic, and then into Russia, Mongolia and China.

The eclipse will occur between about 8am and 1pm GMT, but the exact time depends on where you are on the planet. In the UK, the eclipse will be partial and will last between 9:30 BST and 11:20 BST.

However, from London at most only 20% of the Moon will cover the Sun (as in the image to the left); from Scotland, the Moon will cover up to 40% of the Sun.

The Royal Observatory, Greenwich will be opening at 09:15 in order to catch the start of the eclipse, and with support of the Flamsteed Astronomical Society, the public will have the opportunity to view the eclipse through solar telescopes.

Full details of the eclipse can be found at the NASA eclipse website, or at SpaceWeather.com.

Remember, NEVER look directly at the Sun! Doing so will burn a hole in your retina, blinding you for life. So always use a solar filter, or project the image of the eclipse Sun onto the ground, using your hands like this to project an image like this, or even a scarf like this to project an image like this... or even use a hat!

Below is a time-lapse of the 2005 total solar eclipse, as seen from Egypt.

I have to confess that I wasn't expecting much from this eclipse! Sure, it's always nice to see one, but it was only 22% coverage by diameter (12% by area) over London, we are at a solar minimum (so no sunspots were visible) and the weather forecast was looking uncertain. So would any one even turn up to the observatory to look? Would we get to see anything at all?

Any doubts I might have had, had totally disappeared by 9am! The Sun was shining, people were queuing up outside, and our volunteer helpers from the Flamsteed Astronomy Society were working flat out to set up all the telescopes. There was a fantastic buzz about the place - and the gates had not even opened yet!

From the moment the gates opened, the crowds were in, eager to know more about why eclipses occur, how frequently, how long do they last? And astronomers, both from the Flamsteed Astronomical Society and the Royal Observatory itself, were equally keen to answer all the questions.

And then the Moon began to hide the Sun.

Only a tiny amount at first, but enough for the children gathered to celebrate that they had all been the first to see the eclipse start! There is something magical about watching the Moon glide across the face of the Sun - you are seeing the Moon orbiting the Earth orbiting the Sun!

It may only be a small piece of the Sun hidden from view but it's remarkable that it even happens at all. It was so wonderful to see the Sun, our nearest star, with a piece strangely missing that I had totally forgot about the lack of sunspots!

As the eclipse progressed, visitors to the Royal Observatory from all over the world, of all cultures and of all ages could be seen with smiling faces full of excitement and wonder.

It is always a thrill to see an eclipse, solar or lunar. So when is the next one? Well, we don't have to wait long - there is a lunar eclipse in just 2 weeks time. And from the UK, the Moon will be rising in mid eclipse - perfect for some unique photography.

On Monday, the NASA/ESA Cassini spaceprobe flew just 30 miles (50km) over the surface of Enceladus, and at a staggering 40,000mph! Cassini took numerous images of the grooves that run along the moon's south pole, where jets of icy water vapour erupt hundreds of miles into space.

To see the latest images, take a look at the Cassini flyby of Enceladus internet page, including the image below. For the thoughts of the Cassini scientists, see the Cassini blog.

At 12.03pm GMT today, the poles of the Earth were aligned with the Sun, which is what we call the solstice. While in the Northern hemisphere, the North pole was pointing away from the Sun (it was the Winter Solstice), in the Southern hemisphere, the South pole was pointing towards the Sun (the Summer Solstice), which is why it is winter in the North and summer in the South.

The image below shows a stacked series of images taken 20 minutes apart throughout the 17th December, 2005 (within just a couple of days of the winter solstice), showing how the Sun moved across the sky during that day, from the South-East to the South-West. A timelapse movie version is also available, showing that at this time of year, while the Sun is very low in the sky, the full Moon is very high in the sky.

The Winter Solstice also marks the shortest day, although the earliest Sun-set and latest Sun-set occur on different days (the 12th and 30th of December, 2008).

There are lots of special events to mark the solstice, including a gathering at Stonehenge in Wiltshire (see photographs on the BBC News). Under the early Julian Calendar, the winter solstice actually occurred on the 25th of December, but because that calendar was not accurate, the solstice slipped to the 21st (the accuracy of the calendar was corrected with the introduction of the Gregorian calendar in 1582).

However, we still traditionally keep the 25th of December as the day for celebration, and Christmas now includes a rich mix of celebrations, including Roman (Saturnalia, and Dies Natalis Solis Invicti, the birthday of the unconquered sun), Nordic Pagan festivals and the Christian celebration of the birth of Christ (see more about the origin of Christmas at this Wikipedia article).

Whichever way you choose to celebrate this time of year, we hope you will enjoy yourselves and have a very happy festive season!

Whatever the weather, the Observatory at dusk is always a pretty amazing place to be, not least because of the fabulous views across London. Unlike last night when it was misty, the skies were really clear when I snapped this shot of the Peter Harrison Planetarium on Tuesday.

As it happens we had an Evening with the Stars running that evening and our visitors had a real treat as they looked though the 28-inch telescope. If you are interested in looking through it yourself, there are more sessions scheduled for later this month and into March.

Several of us will be attending Astrofest at Kensington Town Hall at the end of next week. Greg Smye-Rumsby and Richard Dunn are both giving talks on Friday morning (6 February). Greg's is titled: The Universe in three dimensions, whilst Richard's is titled: Spying the stars: The invention and development of the telescope. Richard's new book The telescope: a short history, is published by the National Maritime Museum this March. If you are at Astrofest, do drop in on our stand (stand 20) on the lower floor and say hello.

Today is Chinese New Year and sees us saying goodbye to the Rat and hello to the Ox. But, while most of us are relatively familiar with the idea of animals marking the 12-year cycle of the Chinese calendar, we probably know less about how this calendar works.

It is a luni-solar calendar, meaning that it is based on the apparent motions of both the Moon and the Sun. Because the lunar months (29.5 days) do not match the solar year (365.25 days), there always several days 'left over'. This problem is solved by adding an extra, intercalary month seven times in every 19 years. The Chinese new year moves around (between 20 January and 19 February) in our calendar because it is timed to coincide with the first new moon after the winter solstice.

The 12 animals assigned to the years reappear elsewhere in Chinese calendars and astronomy. They are used to represent the 12 ordinary months, a cycle of 12 days and even two-hour periods within each 24-hour day. In astronomy, the animals are associated with the stations which Jupiter passes through in one revolution around the Sun (an 11.86-year cycle) and yet another association is with compass directions. Chinese compasses and sundials in the Museum collections therefore include the characters for the animals.

Families will get a chance to have a closer look at instruments like this during half-term (20 February 2008) when I will be displaying and talking about them at the ROG. You can find about more about details of this and other Chinese New Year events at the museum.

While looking into the history of the telescope, I've been struck by the number of images that, perhaps unsurprisingly, show it symbolically as an instrument of revelation and learning. One of my favourites is this detail from the frontispiece to Johannes Hevelius' Selenographia of 1647.

Hevelius (1611-87) was from a brewing family from Danzig (now Gdańsk, Poland), gaining further riches from his marriage to Katharine Rebeschke, whose family lived next door. Being so well off, he could indulge his passion for astronomy by building large telescopes for his personal observatory, which spread across the city's rooftops. One of the things he did there was to spend four years making detailed, and very beautiful, maps of the Moon, which he published in the Selenographia. His very fine observing skills and artistic talent, not to mention the quality of his telescopes, meant that these were the best lunar maps available for a century.

This detail from the book's frontispiece symbolically shows how the telescope fitted into his work and thinking.

In the centre is the figure of Contemplatio, covered in eyes and carried aloft by an eagle. Both these figures are significant. 'Contemplatio' can be translated as contemplation, but also as viewing or surveying, while the eagle represents both vision and ascension. Contemplatio is also holding a telescope in her right hand and is using it to sweep away the clouds of ignorance. Behind her are the Sun and Moon as revealed by the telescope, with sunspots clearly visible. Beneath Contemplatio, two putti hold a banner with a biblical quotation from Isaiah, which translates, 'Lift up your eyes on high and behold who hath created these things.' To Hevelius, then, the telescope is an instrument that reveals the truth about a (Christian) created universe, the contemplation of which is a spiritual journey in itself . His telescope is a weapon of intellectual and spiritual advancement.

If you are interested in Johannes Hevelius and his astronomical work, you can find out more at our forthcoming conference, The Long View.

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

You can get information on the visibility of the Moon from anywhere in the world 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.)

• Moonsighting.com - provides moon visibility curves for the current year and next year.
• Astronomical Applications Department of the US Naval Observatory (USNO) - lists New Moon birth times for the whole year. Note, the crescent Moon will not be visible until at least 15 hours after the birth of the New Moon. The USNO also has a page dedicated to the visibility of the crescent moon and the Islamic calendar.
• You can help astronomers improve their predictions by joining in the Moon Watch project. Look out for the new crescent moon and submit the details to the Moon Watch website.

With dark nights around the winter solstice, December is an ideal time for stargazing. Why not come to the Royal Observatory for a special observing evening with our astronomers?

Christmas Sky Watch

Explore the wonders of the winter skies, and gain a useful introduction to the use of binoculars and small telescopes. The session will include a planetarium talk, a short seminar and a practical session.

Date: 11 December 2009
Time: 19.00-22.00
Cost: £15/£11

Christmas stargazing

Part of our programme of observing evenings, these sessions offer you an opportunity to use our historic 28" diameter refracting telescope, the seventh largest in the world. With a chance to look at star clusters and double stars, the programme provides an unusual Christmas experience that's out of this world. Places limited.

Please note: If adverse weather conditions prevent viewing through the telescopes, an alternative programme will be offered. We are not unable to offer refunds under such circumstances.

To book a place

Image: NGC 2264 including the Christmas Tree Cluster (ESO)

Happy solstice from the Royal Observatory, Greenwich! The 2009 winter solstice occurred today (21 Dec) at 17.47. Enjoy the long night - and if anyone in these parts was dreaming of a white solstice, they certainly got one.

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

The Royal Observatory, Greenwich has just launched Solar Season, running until 9 May.

Come and see the Sun in a whole new light with new exhibition Solar Story, planetarium show Secrets of the Sun and a programme of talks, tours and workshops. Speakers include solar physicist Dr Lucie Green and ROG Curator for the History of Science and Technology Dr Rebekah Higgitt.

Then this coming Sunday residents of the UK will lose an hour's sleep to gain an extra hour's daylight in the evenings. Longer evenings are not of course good news for everyone - amateur astronomers will have to stay up later and later to get the darkness needed for observing.

So at 1.00 am GMT on Sunday 28 March clocks in the UK officially move forward by an hour as civil time changes from Coordinated Universal Time (almost identical to Greenwich Mean Time) to British Summer Time or BST.

Which means that though it's definitely now spring, as of next week we'll be in British Summer Time, which this year lasts until 31 October when by most counts we'll be in mid-autumn... it's no wonder we get confused about the seasons.

In search of a bit more clarity, why not listen in to David Rooney discovering more about British Summer Time or have a look at our Spring Forward: 100 Years of British Summer Time page?

Did you know that today - 25 March - used to be New Year's Day in England right up until this country's very late adoption of the Gregorian Calendar in 1752?

25 March in the western church's calendar is the Feast of the Annunciation, commemorating the Angel Gabriel's announcement to Mary that she would be the mother of Jesus. It is also of course near the date of the spring equinox as well as of Easter.

As there's no compelling scientific reason for choosing any particular day as the start of the year, it at least makes poetic and emotional sense to celebrate the New Year at the same time as we're celebrating spring and new life than in the cold midwinter dark of January.

Other notable New Year's Days this year include last month's Chinese New Year, and Al Hijra (Islamic New Year's Day) on 7 December 2010 (1 Muharram, 1432 AH).

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

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

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.

20 December 2011 - At 23.38 UTC (GMT) tomorrow, 21 December, the solstice will occur when the poles of the Earth align with the Sun. In the Northern hemisphere, the North pole will point directly away from the Sun (the winter solstice), while in the Southern hemisphere, the South pole will point directly towards the Sun (the summer solstice).

At the solstices 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. At the winter solstice, the apparent position of the Sun reaches its most southerly point against the background stars.

Shortest day and sunrise/sunset times

The reason for this is the slight variation in the length of 'natural' days throughout the year, resulting from a combination of the Earth's elliptical orbit around the Sun and the tilt of the planet's rotation axis. For clocks to work all days need to have an equal length, which is therefore fixed at the average length of a natural day (hence the 'mean' in Greenwich Mean Time). This has a knock-on effect on sunrise/sunset times, and the earliest sunrise occurs several days before the longest day and the latest several days (about 9) after the shortest.

Opinion is divided over whether the solstice marks the start of winter or the middle of winter, or whether winter actually starts on 1 December (as reckoned by most meteorologists).

Marking the solstice

Solstice shorts: Yuletide stargazing

For an alternative way to celebrate the solstice, why not join us for our 25-minute Yuletide stargazing sessions, daily at 16.30 and 17.00 on 20-23 December? These offer a unique opportunity to look through our historic 28-inch diameter refracting telescope, and to view one of the more striking double stars.

Places are limited and tickets are £6 per person. You can book online or call 020 8312 6608 between 10.00-16.00. (Please note: If adverse weather conditions prevent viewing through the telescopes, an alternative programme will be offered. We are not able to offer refunds under such circumstances.)

Whichever way you choose to celebrate this time of year, we hope you will enjoy yourselves and have a very happy festive season!

21 December 2010 - UK viewers will be able to catch the start of a total lunar eclipse this morning, the first for three years, with totality starting at 07.41 GMT and lasting a little over an hour. Within the UK, Scotland and Northern Ireland will get the best views.

Lunar eclipses occur when the Moon passes through the Earth's shadow. During eclipse, the Moon may turn blood red or pink, with indirect sunlight giving the Moon a ghostly hue. Find out more in our eclipses fact file.

The last time a total lunar eclipse occurred on the winter solstice was in 1638, and the next time will be in 2094.

This year the Royal Observatory will be taking part in Obscura Day, an international "day of expeditions, back-room tours and hidden treasures" developed by the people behind Atlas Obscura. On Saturday 9 April there will be two different curator-led tours on offer. Further details can be found on the NMM events list (here) and should be booked on the Obscura Day website (here - put 'Greenwich' in the search box). Because both tours will include a visit to the object stores of Flamsteed House, numbers are limited - book your place now!

Tour 1: 10.30: Go back in time at the Royal Observatory Greenwich
Take a tour back in time with Dr Rebekah Higgitt, Curator of History of Science and Technology, through the astronomy, buildings and collections of the Royal Observatory. Learn to tell your altazimuth from your equatorial, spotting Victorian terracotta and Tudor vaults on the way.

Tour 2: 13.00: Charting Greenwich Mean Time
Come to the Prime Meridian of the World and explore the collections at the Royal Observatory, Greenwich with Rory McEvoy, Curator of Horology. Discover how Greenwich Mean Time was determined and kept throughout the years and why an observatory should be so closely connected with precision timekeeping. The tour will include a rare opportunity to see some unusual time related objects from the Museum's reserve collection

Meeting place for tours: Shepherd's Gate Clock, main gate, Royal Observatory. Tours start promptly. Please arrive at least 5 minutes before start.

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.

The Astronomy Photographer of the Year competition is back! Now in its fourth year, the competition continues to showcase incredible images from amateur astrophotographers all around the world, featuring beautiful objects from within our solar system and far into deep space.

Anyone can enter - whether you're new to astrophotography or a seasoned amateur, and whatever your age. We've had a huge range of images in previous years, from amazing landscape photography that captures the Moon and the Sun to stunning deep space images taken by robotic telescopes. Find out how to enter and what you could win.

Overall winner 2011: Jupiter with lo and Ganymede,
September 2010 by Damian Peach (UK)

The four main competition categories are Earth and Space, Our Solar System, Deep Space and Young Astronomy Photographer of the Year. The judges will also be awarding three additional special prizes: People and Space, Best Newcomer, and Robotic Scope Image of the Year. Find out more about the categories and prizes.

Entries to the competition close at midday (BST) on Friday 29 June 2012.

The winning images will be displayed at the Royal Observatory Greenwich from September in the free Astronomy Photographer of the Year exhibition. There's still time to see the winning images from 2011 (closes 12 February).

Good luck, and we look forward to seeing your photos in Astronomy Photographer of the Year 2012!