I am trying to find the marriage of Thomas Short and Ann

circa 1820.
On the 1851 Manchester census Thomas is aged 53 born Louth and Ann 53 born Co Cork.
Their children are:
Bridget born circa 1828 Louth
Ann born circa 1828 Louth
Catherine born circa 1830 Louth
Sarah born circa 1831 Armagh
Felix born circa 1833 Armagh
Ellen born circa 1839 Louth
There may also have been older children.
Does anyone know how I could find the marriage of Thomas and Ann?
Margaret