This isn't a large mistake, but I noticed it anyway. At the very beginning when Leo is naming the stars for his teacher, he says one of them is Mizar (I think that is how you spell it), and that it is a double star. He is right that it is a double star, but when the camera goes up to show us the star, you can see two very bright stars and the comet. Mizar is one of the star in the Big Dipper, so you would have seen the easily recognizable constellation along with those stars.