Dunsink Observatory

Dunsink was founded in 1785 on a low hill northwest of Dublin, which was open country then and is now the edge of the city. William Rowan Hamilton ran it for most of the nineteenth century and lived in the house; the walk from here to Broom Bridge, where he cut the quaternion formula into the stonework in 1843, is still a small pilgrimage for mathematicians. The main instrument is a Victorian refractor under a rotating wooden dome, and it is still used on public open nights through the darker half of the year, when volunteers point it at whatever the cloud allows. The rest of the time it is a research site and closed.

What you actually see

• The South Telescope - the Victorian refractor under its wooden dome.
• The 1785 building - the original observatory house on the hill.
• The open nights - winter evenings when the telescope is used by visitors.
• Broom Bridge - a short walk away, where Hamilton carved his formula in 1843.

When to go

Public open nights run in the darker months, roughly October to March, on set evenings that are booked out quickly once released. They go ahead in cloud, with talks replacing the telescope, so treat a clear sky as a bonus rather than the plan. Outside that season there is no public access and nothing to see.

Honest expectations

Dublin's light pollution puts faint objects out of reach, so the Moon, planets and double stars are what the telescope does well. Cloud cancels the actual observing more often than not. It is awkward to reach without a car, cold standing on the hill, and the buildings are working offices rather than a visitor centre with a shop.

Nearby

Phoenix Park and the National Botanic Gardens are both a short drive away.