Town

Birr or Parsonstown

Biorra

Birr's scientific history includes the world's largest nineteenth-century telescope and the pioneering photography of Mary, Countess of Rosse.

Recorded locationBirr or Parsonstown53.09572° N · 7.90729° WInteractive map supplied by OpenStreetMap.
Recorded place location · Logainm.ieOpen in OpenStreetMap ↗

The name

A reliable full-name meaning has not been established here. The recorded Irish and English forms are given without an unsupported translation.

Recorded forms

  • Biorra · Irish · main form · validated name
  • Birr or Parsonstown · English · main form
  • Birr · English · main form

Place & story

Birr and Parsonstown

Birr also appears in historical records as Parsonstown, a name associated with the Parsons family. The family seat became an unusual centre of scientific work, where workshops, instruments and visiting researchers formed part of a country-house estate. The National Library's nineteenth-century photograph of Rosse's telescope preserves the older name in its identification of the instrument as the Leviathan of Parsonstown. The names therefore connect the modern town with the language used in contemporary scientific accounts. [2]

People & connections

William Parsons and the great telescope

William Parsons, third Earl of Rosse, developed the great reflecting telescope in the castle grounds during the early 1840s. The estate's account describes a tube seventy-two feet long and a mirror six feet across. From 1845 until 1914 it was the world's largest telescope. Observations with it revealed spiral structures in objects then described as nebulae. The instrument attracted observers and visitors to Birr, while its construction depended on practical work in the castle workshops as well as on the earl's design. [3]

People & connections

Mary Rosse behind the camera

Mary Field moved to Birr Castle after marrying William Parsons in 1836. Offaly Archives records her financial and practical participation in the estate's scientific projects and her interest in early photography. She experimented with processes that required considerable chemical and technical knowledge, and won a silver medal for a paper negative in 1859. Her work gives Birr a history of image-making as well as of astronomical observation. [4]

A surviving working space

Mary's darkroom survives at Birr Castle. The Science Museum's account describes it as one of Europe's oldest and places her photographic experiments in the 1850s. Early photographs included the telescope, family members and visitors. The darkroom and telescope are complementary remains: one concerned the recording of nearby subjects on sensitive surfaces, the other the gathering of faint light from the sky. Together they make Birr's scientific inheritance unusually tangible. [5]

Geographic information

Place type
Town
County
Offaly
Civil parish
Birr
Coordinates
53.09572, -7.90729
Logainm ID
125000 ↗

Population over time

Birr — Census 2016 settlement footprint

Population within 2016 settlement boundaries

4,674people · 2022

01.3K2.5K3.8K5K 2016: 4,370 people20162022: 4,674 people2022

Both counts use the 2016 settlement boundary, allowing like-for-like comparison. CSO supplies the 2022 count on this older boundary for comparison only. The official 2022 Built Up Area has different boundaries.

View population figures
Birr — Census 2016 settlement footprint — census population
Census yearPopulation
20164,370
20224,674

Source: CSO Census 2022 Profile 1 — Appendix Table 1: Census 2022 De Facto Population for the 2016 Towns · Supporting source 1. CC BY 4.0. Retrieved 2026-10-25.

Other census areas and years

These figures use different area definitions. Read the boundary note before comparing them.

Birr, Offaly — 2011 legal town and environs; 2016 census settlement

Published census settlement populations

4,370people · 2016

Settlement boundaries changed during this period. Differences may reflect boundary changes as well as population change. Where a 2011 legal-town-and-environs count is shown, it has not been recalculated onto the 2016 settlement boundary.

View population figures
Birr, Offaly — 2011 legal town and environs; 2016 census settlement — census population
Census yearPopulation
20115,822
20164,370

Source: CSO E2016 — Population and Actual and Percentage Change 2011 to 2016 · Supporting source 1. CC BY 4.0. Retrieved 2026-10-25.

Birr, Co Offaly — Census 2022 Built Up Area

Built Up Area population, 2022

4,726people · 2022

Built Up Areas use a new land-use definition. Their population figures cannot be compared directly with Census 2016 settlement counts.

View population figures
Birr, Co Offaly — Census 2022 Built Up Area — census population
Census yearPopulation
20224,726

Source: CSO F1015 — Population, Census 2022 Built Up Areas. CC BY 4.0. Retrieved 2026-10-25.

Sources & further reading

  1. Logainm.ie — Birr or Parsonstown. Place names and geographic record, licensed under CC BY 4.0.
  2. Rosse's Telescope photograph — National Library of Ireland
  3. The Great Telescope — Birr Castle
  4. Mary, Countess of Rosse — Offaly Archives
  5. The Remarkable Mary Rosse — Science Museum

Name record retrieved 2026-10-25 · Source record modified 2026-09-19. How this page was prepared.