A Visit to Birr Castle

By Kim Bieler

I have to thank Pete Johnson for giving me the idea to visit Birr Castle. A few months ago he posted a question to the NOVAC listserv wondering how long it would take to drive from Belfast to the site of the "Leviathan" telescope in the Irish midlands. Since I was going to be in Ireland over the Christmas holidays, I resolved to make the trip myself.

It turned out to be a particularly auspicious outing. After five straight days and nights of holiday parties, my husband and I really needed a little time out. And luckily the weather  was perfectly sunny and clear, albeit chilly. But the real surprise was the estate itself—in addition to the great telescope, Birr Castle Demesne boasts a fascinating museum and lovely grounds and gardens. In other words, it's a great place to bring your family members who don't share your enthusiasm for astronomy.

The current castle dates from the 17th century but is built on
The current castle dates from the 17th century but is built on the ruins of a 12th-century Norman castle.

Birr Castle is the seat of the Earls of Rosse, the Seventh of whom still lives in the castle itself (which is not open to visitors). The Parsons family, as they are known, were very involved in science and were early adopters of daguerrotype photography, steam power, and electricity. On the grounds of the estate you can still see a wrought-iron suspension bridge from 1820 and a turbine house built in 1879. Before entering the grounds proper, it's worth spending time in the gatehouse museum which contains a surprisingly large collection of astronomy, engineering, and photographic instruments and artifacts. We were particularly engaged by the brass astrolabes inscribed in arabic, the collection of mid-19th-century photos taken by Lady Rosse, a three-lamp color projector, and a very old static electricity generator. We could happily have spent a lot more time in the museum, if only they had bothered to turn on the heat!

The reconstructed Leviathan, from a distance A closer look at the tube assembly. The Third Earl didn't use a finder scope, but preferred a low-power eyepiece.
The reconstructed Leviathan, from a distance. A closer look at the tube assembly. The Third Earl didn't use a finder scope, but preferred a low-power eyepiece.

It's a short walk from the gatehouse to the telescope, which dominates the bucolic landscape. At 72 inches, the Leviathan was the largest telescope in the world for almost three-quarters of a century. It was built in 1845 by the Third Earl of Rosse, who should be an inspiration to all amateurs who observe under less-than-perfect conditions: despite the fact that Ireland has something like 30 clear nights a year, he spent over £12,000 (the equivalent today of £2 million) on the great telescope and is credited with discovering the spiral nature of the Whirlpool Galaxy. (It should be pointed out that the funds for this project were courtesy of his wife, Mary, who came from a wealthy Yorkshire family. To her credit, she also used her largess to employ over  500 laborers on the estate during the Great Famine.)

The telescope fell into disrepair in the early part of the 20th century, but a full restoration was conducted in the 1990s. Great care was taken to recreate the original design exactly—with the exception of the mirror. The Leviathan's original, polished-metal speculum, weighing 3 tons, was replaced with a modern glass-and-aluminum-alloy mirror, at a fraction of the weight. One of the original mirrors is still on display in London's Science Museum.

Since our visit was very much in the off-season there wasn't  anyone to ask, but the telescope certainly appears to be in good working order. All of the metal parts were heavily greased and the dozen or so seats near front of the structure suggest that periodic demonstrations of the mechanism are held (no doubt at the yearly star party held on the grounds).

It's a truly awesome piece of machinery. The cranks for the altitude and azimuth adjustment are enormous and look like they might have required two people to turn. Thick chains run underground from the cranks and huge counterweights are suspended overhead. Nowadays the apparatus is controlled electronically and with hydraulics, but it's not hard to imagine the Third Earl in his viewing cage high over the ground, shouting out instructions to his freezing assistants below. The walls on either side of the tube, which served as both supports and wind-breaks, constrained the side-to-side movement of the tube such that an object was only viewable for about an hour each night while it crossed the meridian.

One of the giant azimuth cranks.
One of the giant azimuth cranks.

A short walk from the telescope led us to the man-made pond (complete with ducks and a couple of bad-tempered swans), a waterfall and fernery, formal gardens surrounded by a hornbeam cloister, and the tallest box hedges on record. I'm determined to return in warmer weather, because the grounds—while picturesque even in the starkness of winter—would no doubt be spectacular in full bloom.
If you're thinking of visiting Birr Castle, or would like more information about the estate and telescope, they have a comprehensive website at www.birrcastle.com.