This is an interesting question with some reflection. On the surface, rationalism is the belief that there is a reasonable, usually a scientific or mathematical explanation for all things. Superstition within this framework is usually understood to be excessively religious in a negative way or to have an non-rational bases for understanding something.
If we take a step back, these assumptions can be challenged. Some very thoughtful cultural anthropologists and sociologist have challenged these notions. For instance, if more and more people believe in something, then it usually moves from the realm of superstition to religion. There is an element of the social construction of reality in place. Moreover, if we study science, then we will realize that the basis for science is often theories, which later on prove to be false. If they are false, then there is an element of faith. I will attach a summary of the work of Thomas Kuhn, a historian of science.