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The civil parish for Castlemaine is Kiltullagh. The related RC parish would be Keel or Castlemaine. Here is a link to the 19th century parish register up to around 1880 https://registers.nli.ie/parishes/0662 As you can see, baptismal records go back to 1804, however, when I searched the subscription site Roots Ireland the earliest Patrick Moriarty baptismal record in Castlemaine was in 1835. Reading your message, it appears that your Patrick may have been born/baptized before 1804 and thus a baptismal record would not be available.
Let me know if you have any questions.