I seemed to have run into the same problem as George Martin when I looked for the 8TH Michigan. For some reason it is listed as the 1ST Michigan Battery H. But since you confirmed the name of the Captain then it must be the unit.

If I understand you correctly you want to find out where this unit was located on the many battlefields during the Atlanta Campaign. I would suggest you look for the series of books by "Willaim R. Scaife". I'm not sure how many battle of that campaign he wrote.....maybe George knows. I have one of his books titled "The Chattahoochee River Line" and it shows the location of that unit during that action.