had just text info about mars/venus conjunction to a friend. so i was noticing sky- how clear it was but with small amount of haze on horizon (20degrees to horizon) otherwise very clear. object seemed to be at perimeter, and JUST behind this SLIGHT haze. it seemed to move within the haze a few times. it had NO lights but a very dull light gray, metallic appearance. i assume that this was slightly reflecting city lights. it did not emanate any light. you would have to be looking at that particular line of sight to even notice it. it was very light and somewhat masked behind the very slight haze/fog. but absolutely, clearly an object moving along an eastward path in the sky about five hundred feet above the land. it changed direction VERY smoothly and quickly (unlike a plane) and continued in a straight easterly direction. speed was a bit faster than a plane at that same distance but slowed down after direction change then regained original speed. the change in direction was about 3 or 4 lengths of its size- (SFO is about 15 miles away from my location at the time and there was actually a plane at the same distance as the object to the west at 35 degrees to horizon- but not at all close to object.)thought that it could have been a (HUGE!) drone but it had NO LIGHTS. i imagined something THAT large would be legally required to have lights. object moved out of view, never changed in size, shape or detail of outline.it seemed very drone-like. seemed to be surveying(?). i was shocked at what i was seeing. i tried to take a picture with my iphone5 but screen would not accept my touch.(%$&*ing i-phone screens) object was the size of three large airplanes put together if each airplane filled out their respective full diameters.it felt "unmanned" until it changed direction which of course seemed to indicate that a decision was being made by something to change direction.