Did you notice the object in the sky before you photographed it or did you notice it in the photograph you took? If you noticed it before you took a shot, it could be the small vapour trail of a high flying aircraft reflecting sunlight. Being just after sunset it would have been lit by the sun despite a darkening sky. If you noticed it only in the shot after you took it, then yes, I agree with the previous posts, it will most probably be internal lens/ filter reflections.
|