A ring of light appeared, filled in with golden light, increased in brightness while moving, then gradually faded away.

A thin, perfect circle of silver light appeared northeast of my position.  As I observed the circle, it began to fill in with a faint golden light.  The light filled in the circle with irregular "rivulets" of golden light until the circle glowed a uniform golden color, not unlike that of a full moon except that it was perfectly uniform with no "craters" or surface imperfections.  It was about the size of a nickle held at arm's length and about 30-35 degrees off the horizon.  I had a clear view with no obstructions.  The circle of golden light was well defined at first.  It then began to slowly increase in brightness until it appeared to "boil" with the boundaries becoming indistinct.  It then began to move in an arc toward the North maintaining a uniform elevation above the horizon.  I then began to notice that it was decreasing in brightness slowly as it moved.  It lost brightness uniformly until it was once again a distinct circle of light.  It continued to slowly move toward the North until it was no longer visible.  It moved a total of approximately 40 degrees of arc in 10 minutes or so.  No sound was apparent.
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Date is approximate.  PD))