The size of the object and it's perfect detail left us with no doubt of what we were seeing.

Sorry about informing you about this 19 years after the fact.  Anyway, I thought you might want to hear about what my brother and I witnessed.
From our vantage point from a mountain northeast of Santa Rosa we spied the object perfectly sillouetted against a river of fog luminated by a full moon that was flowing across the entire valley below.I would quess that we were about seven miles away as the crow flies. I make that assumption based upon my knowledge of how far the city of Sabastopol is from Santa Rosa. Using the lights of Sabastopol peaking through the fog as a measuring stick I would have to say the object was close to being at least a mile across.Now unlike other alledged sightings this object did not have any flashing lights.I thought it strange that it wasn't illuminated like the fog or lit up at all.It was like light had no affect upon it. It was  flat dark grey in color.It had a dome on top and bottom. Hollywood movie makers could not have created a more perfect saucer,only this one was real. We looked at it for about two hours before getting bored and to cold to look at it anymore, then went home. All the time we were watching it, it didn't do anything.  It just sat motionless above the fog as the fog flowed beneath it.
Witness is public employee.  Date in 1974 is approximate.  PD