Heliometer building, Old Observatory, Leiden

Tucked inside the botanical gardens of Leiden University in the Netherlands, the Heliometer Building is a small domed tower that once housed one of the observatory's specialised instruments for measuring the positions of stars.

About the Heliometer Building

The building stands on the grounds of the Old Observatory of Leiden, one of the oldest university observatories in the world, and is operated today by Universiteit Leiden as part of a heritage site open to the public.

History

The Heliometer Building was constructed in 1878, decades after the main Old Observatory building was completed around 1860. It takes its name from the heliometer, a precision instrument originally used for measuring small angular distances, such as the apparent diameter of the sun and the separation between stars.

Telescopes & research

The Old Observatory site is home to the 48-cm Zunderman Reflector, a telescope used historically for photometric observations of variable stars, tracking how their brightness changes over time.

Location & getting there

The building sits within Leiden's Hortus Botanicus area in the Netherlands, close to the university's historic city-centre campus, making it an easy stop for anyone exploring Leiden on foot.

Visiting the Heliometer Building

The Old Observatory site, including the Heliometer Building, is open to visitors from April to October on Saturdays and Sundays, 10:00 to 18:00, and from November to March on Saturdays and Sundays, 10:00 to 16:00. Wheelchair access is limited, so visitors with mobility needs may want to check ahead with the university.

See your named star from here

Leiden has one of the longest running astronomical traditions in Europe, so it's a fitting place to think about your own named star. Look up its coordinates in our star catalogue before your visit, and see how it sits among the stars this historic site has studied for well over a century.