bronze, bright, silent light moves south to east over a lake in Maine.

I was playing hide and seek in the evening with cousins visiting from California and went and sat down by our lake (Three Mile Pond, facing south) in a lawn chair.  While there, I noticed a bright light that had a bronze tinge on the horizon across the lake.  
First I didn't think anything about it, but then I noticed it was rising up off the horizon, and was moving.  I began to watch it.  It was totally silent, it rose high up then seemed to move across the lake high overhead.  At the largest, it was about the size of my thumbnail at arm's length in the sky. 
I watched it until it went toward the eastern side of the lake where there was a full moon on the rise just over the tree tops.  The light from the moon was so bright I lost sight of it.  
I told a friend of mine the next day and she said it had to be a weather balloon, but I had never seen one before or after that.
Witness indicates that the date of the sighting is approximate.  PD