Living in a busy air corridor (SFO, OAK, etc.) -- and having already seen a UFO (daylight sighting, cigar-shaped craft) from the same location -- I keep my eyes open. This was a night sighting, from the windows of our two-story house. I took notice of this object out my bedroom window as it seemed big, but was moving far too slowly to be a jet aircraft -- and was far too big, easily 3-4 times larger than the typical outline of jet aircraft navigation lights. I called my boys, aged 7 and 9, to view this and we all ran to watch from another window as the object moved slowly behind a tall pine tree (about 100' tall on one corner of the property). The object was heading southeast, then changed direction in a slow curve to due east, lazily moving right past my house less than a half-mile away. It moved right over the main part of town, banked slowly south for approx. 1/8th of a mile, then back on a due east course, heading toward Berkeley across San Francisco Bay. We then lost sight of it through the trees, as it was quite low (no more than 1000 feet). It was then that my wife got home from work and said that she'd seen the object as well from her car, thinking it looked big, and had rather odd lights for an airliner. She also remarked that it made no noise whatsoever, while jets flying past are often quite loud. My boys then said that THAT was the object they'd seen before in the general vicinity.