I discovered an Eleanor Harbison, married to a 'Peter Kergan', in the tiny (1000 acre) townland of Tintagh, on the slopes of the Sperrin mountains, a few miles northwest of Moneymore. Most of the townland is mountain, and settlement was clustered in the southeastern corner. The names are misspelled repeatedly in the Lissan parish register. There are three Cargans in the 1827 Tintagh tithe applotment book, and more in the 1831 census, along with a Cargin; two Kerrigans, John and Patrick, in the Griffith's valuation for about 1860; and Carrigan and Carigan families in the 1901 census. This was obviously a result of illiteracy, but it makes the names difficult to search.
It looks like a desperate place to live; how they survived the famine is a mystery.
Eleanor was most likely one of the previously unidentified daughters of Francis Harbison (1795-1837), since two of the three witnesses, Lucy and Jane, were either Francis' spouse or his daughter.