If I were to photograph my new home and in one out of ten pictures appears to have a single orb, just one in the middle of the shot and large, does that cancel out the dust and water theories? Or can it appear with on partical and be a false orb? What can I make of one orb caught in only one photo?
Unfortunately I don't think there's any way to tell 'real' orbs from false ones. Personally I would assume the orbs are caused by dust etc unless there were other phenomena happening. And even then I'd be very careful about interpreting my photos.