Aspherical lens elements may be more normal today, but the this lens was released in the late 70's. The aspherical element on the Noct was hand-ground as opposed to stamped by a machine. It was always a special-use lens and it was always expensive. The priority of the design was to control coma flare, making the lens more suitable for night photography.
Originally Posted by msbarnes
I have a 50mm f/1.2 that I have a love/hate relationship with. I don't know if I would prefer the Noct or not. Probably not.
Edit: Mr. Waves beat me to it. Do reference the link below if you want to read more about the Noct: