QUOTE (toddbronco2 @ Dec 23 2010, 03:01 PM)
It's not clear from the video whether the moon moves in front of Neptune or behind it so I don't think you can conclude that the orbit is retrograde (i.e. Triton's) without more info
I agree with Phil. Furthermore from the few frames of the movie it seems that curvature of the moon's orbit is that of the object in the foreground in the roughly equatorial orbital plane.
Edit: I'm not so sure now. I'm thinking it might have been one of the smaller moons closer to the planet. Size of Triton's orbit would make it unlikely to be captured in the same frame as Neptune.
Edit #2: I did some calculations and it seems that that moon moves far to fast for it to be Triton (whole animation is of 6 hours of Neptune's rotation). I would guess that moon must be one of the closer ones to the planet (Naiad perhaps?)