I observed a green,circular light travel across my field of view while near a potato field at night.

At the time of my sighting, I was a two-year veteran of the USAF.  My home of Caribou, Maine, at the time, was home to Loring AFB, a Strategic Air Command base.  I have since retired from the Air Force after 21.5 years.  The area is extremely rural and remote, Caribou being the largest city in northern Maine.  I had returned home on leave and was out on a date.  We parked near some railroad tracks and had a view of the horizon, as created by hilly potato field.  The sun was down but you could make out the horizon line.  I saw a circular light approximately the size of a dime held at arms length, travel across my field of vision, above the horizon line.  It was green, hazy on the edges and traveled across my field of view and disappeared below the horizon in 5 to 10 seconds.  Being familiar with aircraft and having seen numerous meteorites in the area, I determined that it could not have been either.  It moved to slow to be a meteorite and had no characteristic lights that would mark it as an aircraft.  No sound was heard.
Witness indicates that date of the incident is approximate.  PD