McCusker/McOsker/McOscar

I am going to be in County Tryone in late March of this year.  I am looking to find exactly where several great grandparents were born and lived before coming to the States

My one great grandfather was John McCusker (here in NYC that is how the name was spelled) I know he married Alice Donnelly of Altaglushan on 10 May 1893 and they left immediately for NYC.  I have them entering NY on 22 May 1893. On the marriage cert his last name is written as McOscar and on the ship's manifest it is written as McOsker.

My maternal grandmother, their daughter Margaret, always said that her father was an only child.  Unfortunately her mother Alice Donnelly McCusker died in Feb 1902 just before Margaret's 5th birthday.  Her father John died in 1906. 

I have found on RootsIreland and looking at marriage certs online on PRONI - that John was born July 1870.  His baptism record shows baptism on 31 July 1870 with father John Irwin and mother Rose McCusker.  It also states that the child (john) was illegitimate.  According to the marriage cert John listed his father as John Irwin but then there is a notation "the boy says he took his mother's name."  The baptism record shows address at time of birth as Ballynahaye.

I know nothing else about him since my grandmother was only a round 9 at the time of his death and was actually living with her mother's cousin and her family at the time.  The oldest child Rose Ann had been sent to Ireland to live with her Donnelly grandmother. The two youngest children John and Alice went to live with an aunt in NYC.

On the marriage certificate, John lists his address as Altaglushan.

Any information or direction as to where to look next is greatly appreciated.

Thank you

Joanne Walsh