The current shader uses only one calculation direction, for performance and SM2.0 compatibility. This means that i can have moon glow only after sun calcs are done, this is why i fade out the sun and smootly bring in the moon glow. The effect is smoother in a normal day cycle speed, in the fast mode seems to glow suddenly indeed, but it can be regulated to do a smoother transition in the fast speed as well if needed. The idea was that the moon glow wont come into play until the sun ambience is gone, so it would make sense to optimize this way. I will add a shader version that will calculate both sun and moon glow at the same time and optimize for SM2.0 in the next version, so they can work independently. Also i will try to regulate the glow appearence/dissapearence better for the faster cycle too. Maybe it needs some extra tweaking in the timing and speed of the sun effect fade and moon glow appearence to get it better synchronized.