If the individual was not found, at least you have the names of the parents and the location. The records for the six counties of Northern Ireland are on microfilm at the Public Records Office of Northern Ireland, however, they can also be found at Ancestry, 1841/1851 Census Abstracts (Northern Ireland). For the six counties the images were taken from a book by Josephine Masterson, and published by Genealogical Publishing Co. in 1999.