I was hiking the bill wallace trail in el capitan state park taking high resolution photographs with my canon eos 40d digital camera with telephoto lens. i took a photograph of the exxon-mobil las flores canyon petroleum processing facility about one mile to the west. upon reviewing my photographs later that evening on my laptop i noticed that i had unknowingly captured a strange, brown colored missile shaped aerial object hovering or flying over the facility. it is visible in the upper right quadrant of the photo. i would have dismissed this object as debris on my lens if the follow-up photo i took six seconds later had also shown the same object in the same frame area. it did not, and this artifact does not look like camera lens debris. the object appears to have been captured in motion about 900 feet above the facility heading south toward the pacific ocean. i did not see, hear or sense this object at the time i took the photograph.