|Character||Fl WR 15s.|
|Sectors||R195°-307° (112°), W307°-195° (248°)|
|Light Range||White 18 nautical miles, Red 14 nautical miles|
|Height of Tower||20 metres|
|Height of Light above MHWS||35 metres|
Statutory sanction for a lighthouse to be built was given by Trinity House after the Ballast Board had informed them that tolls would only be levied on local shipping using the light and not Atlantic vessels.
Plans were prepared for a tower and two dwellings, and acquisition of the land required went ahead. Two years later five proposals were received for building the premises and that of Mr James Aiden was accepted for £958. The copper dome was fitted on the tower during the summer of 1846.
Unfortunately extant records do not reveal why ten years elapsed before the light was established. The second order dioptric apparatus flashing white to seaward and red towards the land with a character of one flash every twenty seconds, 116 feet above high water, was first lit on 14 April 1856. The circular tower, 65 feet high) was unpainted grey limestone (from Sligo) with the lantern and dome painted red. The total cost at the time the light established was £17,419:2:6.
Sometime during the late 1860s or early 1870s the tower was painted white with a red lantern and dome. The red dome lasted until 1935 when the complete tower was painted white.
The optic was removed to Aranmore in 1864 and replaced by a first order catoptric system of lamps and reflectors from Tory Island. The character was altered from flashing to fixed white and red on 1 June 1864. This switching of optics was due to the re-establishment of Aranmore which had been discontinued in 1832 when Tory Island Lighthouse was established.
A further optic change took place on 1 January 1894. The light was made flashing again with one flash every fifteen seconds. The dioptric lens came from Inishtearaght supported on a new pedestal with a six wick burner. This burner was replaced in 1908 with a paraffin vapour burner.
Towards the end of 1907 shore dwellings were proposed. A site in Glencolumbkill was purchased in May 1909 and a terrace of four houses built. The Keepers and their families moved in around Christmas 1912. Until then the families had lived on the island with the Keepers. Forty five years later the shore dwellings were discontinued and sold in September 1957.
Irish Lights first step into the atomic era was in 1964 when the UK Atomic Energy Research Establishment at Harwell, Buckinghamshire, asked for their views on isotope powered thermo-electric generators in the marine lighting and navigational field.
Meetings were arranged between Trinity House, AERE, and the Research and Development Section of the Lighthouse Authorities, and in October 1968 Blackrock Mayo was chosen as the lighthouse which, for experimental purposes, was to have one of these isotope generators.
In a report dated July 1970 the Engineer-in-Chief, Mr A. D. H. Martin, stated that AGA Signals Ltd were designing an optic but pointed out that it would be difficult to maintain the present candle power in the horizontal beam if they were to divert some of the light downwards due to the focal plane of Blackrock being 282 feet above sea level. This problem was solved by Inspector of Lights and Marine Superintendent, Capt. C. L'Estrange, who suggested Rathlin O'Birne as being an easier station from the access point of view and only 116 feet above sea level. The Board approved this recommendation.
The isotope generator known as RIPPLE X (Radio Isotope Powered Prolonged Life Equipment-Mark Ten) was transported by road to Holyhead from Harwell, lifted aboard ILT Isolda, cleared customs at Dun Laoghaire and landed directly on Rathlin O'Birne on 7 June 1974. The whole journey from Harwell to Rathlin O'Birne took four days.
Two electric temporary lights were positioned on the lantern balcony railing and came into operation on 20 June flashing white and red every 20 seconds. The old optic pedestal and incandescent gear was removed and a new PRB24 optic was installed.
Irish Lights's only, and probably the world's most powerful, nuclear powered light came into operation on Thursday 15 August 1974. Its character was flashing white and red every 20 seconds and its nominal range was white 22 miles, red 18 miles.
The revolving main light consisted of an array of twelve parabolic mirrors each of which had a 36W, 12V halogen lamp at the focus. Only one lamp was in operation at a time, running off a battery charged by the RIPPLE X generator rated at 33 watts.
If for some reason the main light failed, the two standby lanterns mounted on the balcony railing came into operation but at a reduced power. These lights were electric operating from another battery automatically charged by a Lister LR2 generating plant.
The Keepers were withdrawn from the station at the end of September 1974 and an Attendant was appointed.
A radio link between Rathlin O'Birne and the shore monitored the equipment and when the Attendant pressed a button a signal was transmitted from the station indicating up to seven conditions to inform him of what was happening.
By May 1987 the power output of the RIPPLE X generator was insufficient to power the Rathlin O'Birne light and it was replaced by two Aerowatt 150W wind generators. However, in 1991 the Aerowatt company ceased to manufacture or provide technical support for low powered wind generators. As a result, it became difficult and costly to maintain the wind generator on Rathlin O'Birne. In addition, the PRB24 optic was in poor condition and needed complete and costly refurbishment or replacement.
A solar panel array, batteries, and a sealed rotating PRB46 Mk II optic were purchased for evaluation as a renewable energy powered light system with the potential for replacing wind generator equipment at various lighthouses.
The test solar system performed satisfactorily over a two year period, and it was decided to install it at Rathlin O'Birne. It was decided also to renovate the accommodation on the island which had not been used since the station was unwatched in 1974.
Work on upgrading the dwelling was completed in March 1993 and the installation of the solar system then commenced.
The scope of the project is summarised as follows-
• Adapt existing buildings to provide new battery, electrical equipment and engine rooms.
• Relocate the existing generator set to the new engine room and fit total flood fire protection.
• Fit and commission a temporary optic with a range of 13 nm white and 11 nm red.
• Remove the existing optic and install the new PRB46 Mk II optic.
• Install the new solar panel array on the south side of the tower.
• Install the new batteries, the power control and distribution system, and the aids to navigation control equipment.
• Install the wiring for the station electrical systems.
• Install two new fuel tanks and transfer pumps.
• Install RCMS equipment at the station and at St John's Point (Donegal) shore base.
• Install station security equipment.
The shore base for helicopter operations was moved to St John's Point (Donegal) Lighthouse.
Installation of the equipment was completed and the new light came into operation at sunset on 3 November 1993. The character of the new light was flashing White and Red every 15 seconds, with a flash length of 0.3 seconds. The ranges of the light were white 18 nautical miles, and red 14 nautical miles. The red and white sectors were unaltered. The light and other equipment were linked to the Datac remote control and monitoring system which operates from a central system at Dun Laoghaire, via a sub-central remote telemetry unit at St John's Point (Donegal) Lighthouse.
A radar beacon (Racon), code identification Morse 'O' also operating by solar power was established at Rathlin O'Birne Lighthouse on 27 January 1994.