How to make Space Mountain in Roller coaster tycoon 3 darker

For some reason, when I make my Space Mountain ride, I can see the track, unlike most of the other Space Mountains I have seen. Can someone please tell me what I am doing wrong???

This might sound obvious, but did you try switching the game to nighttime? As far as I know, the game isn't smart enough to make rides that dark during the day even if they're enclosed.