civil war puzzle

[pwh74]

I have seen a photograph of one of my ancestors who was born in  New York in 1820 in the uniform
of an officer in the Union army  in about 1862,.He came to Australia via England but returned to
America to marry in Philadelphia where the photo appears to have been taken. He was certainly
back in Australia before the end of the Civil War. Can anyone tell he how i could find out more
about this?

                                  pwh74

[Erato]

Rosters Of The New York Volunteers During The Civil War

https://museum.dmna.ny.gov/unit-history/conflict/us-civil-war-1861-1865/rosters-new-york-volunteers-during-civil-war

[shellyesq]

This has a database that covers soldiers from throughout the nation - https://www.nps.gov/civilwar/soldiers-and-sailors-database.htm 

If he served with another state aside from New York, there are various links by state here - https://www.militaryindexes.com/civilwar/index.html