Are there any rituals for Nyx the goddess of night?

Yes there are some rituals. Most of which are more or less violent in nature. But if you are just trying to get in touch with Nyx in a spiritual way try casting a circle. You need something of essence to represent the 5 elements, preferably candles. Call first opon Air in the east then move counterclockwise to Fire, then Water, then Earth and ending with spirit. After the circle is cast you may speak to the goddess but be respectful. The goddess may or may not acknowledge your voice, do not force yourself opon her. Be wary that she is related to many other gods and goddesses with affinities to doom, death, sleep,ect. And remember to always close your circle after you are finished. Go the same way you did to open the circle. Air, Fire, Water, Earth, Spirit. A sacrifice, in the reference of blood is also used in the beginning of the casting to show Nyx you are ready and willing. This sacrifice isn't nessisary but it is used in traditional rituals. And also remember to start a ritual with "merry meet" And end with " merry meet, merry part, and merry meet again" I have gotten notice that a ritual like this has been wit ten about in a popular book series The House of Night. And no I did not get this ritual from that book.