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I know that Michael Deegan was born in October 1877 in Corbally. His father was Michael Deegan , a farmer, and mother Jane, nee Dunne.
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what are the other district details on the cert ?
As well as the place of birth, and father's residence, there should be mention of a Superintendent Registrar's district, and also a Registrar's or Dispensary district. These details for these two would help narrow down which townland of Corbally your Deegan family lived.
The Superintendent Registrar's district would probably be Athy, Mountmellick or Abbeyleix.
It looks like your Michael was registered in Mountmellick district, in which case the Registrar's district would probably be Clonygowan, Emo, Cooltrain, Maryborough (Port Laoise), Mountrath or Mountmellick. The remaining Registrar's district in Mountmellick Superintendent Registrar's district is Clonaslee - which would fit with those extracted civil birth records mentioned by annclare. These often give a district, or sub-district as place of birth so could be siblings of your Michael. (note - the extracted births do not contain all records)
John Digan / 5 Mar 1865 / 601 , Clonaslee, Queens Co.
Jane Digan / 11 May 1868 / 610, Clonaslee, Queens Co.
James Digan / 10 May 1872 / Clonaslee, Queens
A research cert for one of the children mentioned would show additional details to confirm if these are in fact siblings - by checking the townland name, father's occupation etc, but given the fact that parents names match (allowing for a variation) the birth cert you have, and the area looks like it matches, I would say very likely siblings to your Michael