Ancient Monuments

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Remains of Astronomical Observatory at Penllergaer

A Scheduled Monument in Penllergaer (Penlle'r-gaer), Swansea (Abertawe)

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Latitude: 51.6737 / 51°40'25"N

Longitude: -3.9933 / 3°59'35"W

OS Eastings: 262264

OS Northings: 199095

OS Grid: SS622990

Mapcode National: GBR GX.7QR2

Mapcode Global: VH4K2.Q6R8

Entry Name: Remains of Astronomical Observatory at Penllergaer

Scheduled Date: 8 May 1980

Source: Cadw

Source ID: 144

Cadw Legacy ID: GM410

Schedule Class: Education

Category: Observatory

Period: Post Medieval/Modern

County: Swansea (Abertawe)

Community: Penllergaer (Penlle'r-gaer)

Traditional County: Glamorgan


The monument consists of an observatory, a building containing celestial telescopes in which astronomical phenomena may be observed. The observatory was constructed in 1846 by John Dillwyn Llewelyn. It comprises a circular stone built telescope chamber measuring 5.5m in diameter. In the centre of this is a conical drum which supported the telescope and a rectangular chamber with vaulted roof abuts on the east side. The chamber is made out of triangular hollow brick. The use of this unusual material was probably to insulate or perhaps to decrease any vibration which would affect the operation of the telescope.

The monument is of national importance for its potential to enhance our knowledge of scientific techniques and processes. It retains significant archaeological potential, with a strong probability of the presence of associated archaeological features and deposits. The structure itself may be expected to contain archaeological information concerning chronology and building techniques.

The scheduled area comprises the remains described and areas around them within which related evidence may be expected to survive.

Source: Cadw

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