The old Greenwich Royal Observatory was designed by Christopher Wren in the 17th century. Two centuries later it became the place where time begins, the Prime Meridian of the world, 0° of longitude. Besides being of historical interest, Greenwich is a leader in bringing astronomy to the public, in part through the Peter Harrison Planetarium.

The planetarium
Planetarium buildings have traditionally echoed features of an observatory. But if you expected a building with a dome, Greenwich's 21st century planetarium would be a surprise. The header image shows the Peter Harrison Planetarium, which opened in 2007, and it's shaped like a “truncated cone”. [Photo: Mike Peel/Sygic Travel]

Forty-five tons of bronze cover the building. As planetarium presenters like to point out, you won't get a signal on your phone through that. (But you're still asked to switch off devices so that the light doesn't interfere with the show.)

You can see from the photo that the structure is tilted. The degree of tilt to the horizontal is 51.5°, which is the latitude of Greenwich. The line on the roof is a narrow gully that runs parallel to the Prime Meridian. The planetarium is near, but not on, the meridian. However, visitors can see a segment of the meridian line in the courtyard of the old observatory nearby.

Have a look at the other side of the planetarium. You can see a second gully there. This one points to Polaris the north star. [Photo: Jennifer Claydon]

Inside the planetarium there are 120 reclining seats under its interior dome. Digital lasers create the images that are projected onto the domed ceiling by a fisheye lens.

Meet the Neighbours Planetarium Show
When I visited Greenwich in August 2017, I saw Meet the Neighbours Planetarium Show. It was presented by one of the observatory astronomers, and designed so that the audience could make choices about exploring some planets in more depth.

The narrative included a look at how constellations were used as guides, and we were reminded that the Sun is a star. We saw not only the Solar System planets and their moons, but also icy objects beyond Neptune, and heard about the possibility of a distant Planet 9.

A father and two children sat next to me. One child was about five, and was entranced with the show, voting enthusiastically for his choices. (We voted by clapping.) The other was younger, and ended up curled up in the seat, sound asleep. Something for everyone.

Other presentations
I've been saddened by planetariums that now show only films, making the planetarium into a glorified movie theater. However the Harrison Planetarium has a variety of shows.

Solar Superstorms revealed drama, violence, and the secret life of the Sun. There is footage of the Sun's surface plus supercomputer visualizations of the interior. The film is narrated by actor Benedict Cumberbatch.

The Sky Tonight looks at the sky for the next month, the sort of traditional planetarium offering that I still like. This is led by one of the observatory astronomers.

A special show for the under-7s was Space Safari. “Join Ted the Teddy Bear on a journey throughout the Solar System, looking for the Great Big Bear in the sky.” It's billed as “interactive with music and rhyme”.

The astronomy center
Complementing the planetarium is the neighboring South Building. The brick and terracotta South Building was built near the end of the 19th century to house telescopes and the observatory's work in astronomical photography. Now it has been turned into an astronomy center, containing the Weller Astronomy Galleries and the Lloyd’s Register Educational Trust Learning Centre. The former is open to the public and the latter is used for workshops for school children and other groups. There's also a nice cafe and shop there, and you can touch a 4.5 billion year old meteorite.

The Altazimuth Pavilion
Looking back at one of the earlier pictures of the planetarium, you also get a glance of the 19th century Altazimuth Pavilion. Originally it contained instruments for measuring the positions of celestial objects. They combined the vertical (altitude) and the horizontal (azimuth) measurements to produce the altazimuth. The building now houses an exhibition about the Sun on the ground floor, and some historic instruments on the floor above.

The Great Equatorial Telescope
Not far beyond the Altazimuth Pavilion is the Great Equatorial Telescope, one of the biggest refracting telescopes in the world. No longer a research telescope, it's used for public night observing and some daytime viewing if weather permits.

Astronomy Photographer of the Year and other events
In September of many past years the ceremony for the Astronomy Photographer of the Year awards has been held at the planetarium/astronomy centre. The courtyard and spacious foyer of the planetarium serve to greet attendees. The winners are then announced in the planetarium itself. And within the Weller Galleries the winning pictures are on display. Visitors to Greenwich will then be able to see them for a number of months after that, and they can also be viewed online.

I noticed that the venue can be hired for special occasions. Just the place for a wedding reception for astronomy buffs! But it would probably be a pricey destination wedding for someone not living in Greater London.

NOTE: I paid for a planetarium ticket with my own funds.