The Portsmouth Harbor Light is one of only two New Hampshire lighthouses in the Atlantic Ocean. There are three small lighthouses in Lake Sunapee, NH. The other Atlantic lighthouse is off shore on the Isles of Shoals. The Portsmouth Light is located on the ground of the revolutionary war fortification Fort Constitution whose ground can also be explored. The light is open for tours on select days in the summer, see the schedule here. Most people will see the light from the grounds of the fort. There are not many good sight lines available, your best option for photos would be from a boat. Check out options for a boat cruise to the lighthouses of New Hampshire here.