Why is my vision fuzzy when I am looking at the night sky?

Less light. At night your pupil dilates in an attempt to permit more light to enter your eye and impact your retina. The center of our vision is the macula where our more precise "cone" photoreceptors reside and permits us to see well in light. Our peripheral retina has less precise "rod" receptors that are more exposed at night when our pupil dilates. This is why your vision is "fuzzier" at night.