Fastnet Lighthouse

Fastnet Lighthouse is a 54 m lighthouse situated on the remote Fastnet Rock in the Atlantic Ocean. It is the most southerly point of Ireland and lies 6.5 km southwest of Cape Clear Island and 13 km from County Cork on the Irish mainland. The current lighthouse is the second to be built on the rock and is the tallest in Ireland.

First lighthouse
Construction of the first lighthouse began in 1853, and it first produced a light on 1 January 1854. The lighthouse replaced an early one built on Cape Clear Island in 1818, partly motivated by the loss of an American sailing packet, Stephen Whitney, in thick fog during November 1847 on nearby West Calf Island causing the death of 92 of her 110 passengers and crew. The new lighthouse was constructed of cast iron with an inner lining of brick and was designed by George Halpin. Costing £17,390, the tower was 63 ft tall with an 27 ft lantern structure on top, giving a total height of around 91 ft. It had an oil-burning lamp of 38 kilocandelas; in contrast, modern lighthouses typically produce 1,300 kilocandelas. In 1883 an explosive fog signal was installed, which electrically detonated a small charge of guncotton every five minutes.

The tower proved to be too weak since gales shook it to the point that crockery was sometimes thrown off tables, and at one point a 60 impgal cask of water lashed to the gallery 133 ft above high water was washed away. Various steps were taken to strengthen the tower, including fitting a casing around the bottom section up to the second floor and filling it with stone, and the surrounding rock smoothed over. In 1865 the lower floors were filled in with solid material.

Second lighthouse
In 1891 the Commissioners of Irish Lights had resolved that the light was not sufficiently powerful, particularly for the first landfall for many ships crossing the Atlantic. The replacement was constructed of stone, cast iron now being considered unsatisfactory – the whole of the nearby Calf tower above its strengthening casing had been carried away during a gale on 27 November 1881, although without loss of life. On the same day, the sea had broken the glass of the Fastnet Rock lantern. The new lighthouse was designed by William Douglass and built under the supervision of James Kavanagh. Construction started in 1897 with the levelling of the site, and the first of 2,047 dovetailed blocks of Cornish granite was laid in June 1899. As well as these blocks, weighing 4300 LT in total and with a volume of 58,093 ft3, a further 4,100 ft3 of granite was used to fill the inside of the tower up to the level of the entrance floor, 58 ft above high-water mark. A small steamship, the Ierne, was specially constructed for carrying the blocks out to the island, and Kavanagh personally set every stone, which weighed between 1.75 and 3 LT. The new lighthouse entered service on 27 June 1904, having cost nearly £90,000.

The masonry tower is 146 ft high, but the focal point of the light is 159 ft above high-water mark. The base of the lighthouse is 52 ft in diameter with the first course of stone 6 in below the high-water mark, and the first ten of the 89 courses are built into the rock. The first floor of the original tower remains, on the highest part of the rock, having been left when it was demolished and converted into an oil store.

The fog signal was changed to one report every three minutes in 1934, and from 1965 accompanied by a brilliant flash when operated during darkness. The original vaporised paraffin light was replaced with an electric one on 10 May 1969. At the end of March 1989, the lighthouse was converted to automatic operation. It is monitored and controlled using a UHF telemetry link to Mizen Head Lighthouse in County Cork, and onwards by landline to the Irish Lights control centre at Dún Laoghaire.

It produces a 0.14-second white flash every five seconds, with a nominal range of 27 nmi and a power of 2,500 kilocandelas. Since April 1978 in addition to being operated during darkness, the light is also used during poor visibility. In 1974 the explosive fog signal was replaced with an electric foghorn producing four blasts every minute at 300 hertz with a nominal range of 3.9 nmi. Following a review of navigational aids, the fog signal was permanently shut down on 11 January 2011. The racon (radar transponder beacon) has transmitted the Morse code for the letter G since its installation in 1994.

In 1985, the lighthouse was struck by a rogue wave about 157 ft high.

On 16 October 2017, a wind gust of 191 km/h was recorded at the lighthouse, during Hurricane Ophelia. This is an Irish record, based on measurements going back to the 1860s. The previous record was 181 km/h at Malin Head during Hurricane Debbie in 1961.

Fastnet Rock
Fastnet Rock (Carraig Aonair) or simply Fastnet (possibly ),  is a small clay-slate islet with quartz veins, and rises to about 30 m above the low water mark and is separated from the much smaller Little Fastnet to the south by a 10 m channel. Fastnet is known as "Ireland's Teardrop", because it was the last part of Ireland that some 19th-century Irish emigrants saw as they sailed to North America.

Fastnet also gives its name to the sea area used by the Shipping Forecasts transmitted by the BBC.

Fastnet Rock is used as the midpoint of one of the world's classic offshore yachting races, the Fastnet Race, a 1126 km round-trip from Cowes on the Isle of Wight, around the rock and back to Plymouth (from 2021 onwards, back to Cherbourg in France). It is also sometimes used as a mark for yacht races from local sailing centres such as Schull, Baltimore, and Crookhaven.