For a naked-eye observer who watches the moon-rises the rise position changes over the course of a "month". If we start at the most northly position, the rise on successive days moves farther south on the eastern horizon until the most extreme southern position for that "month" is reached. Then the rises occur a bit farther to the north each day until we are back at the extreme northern position again.
My question: What is the length of this version of a lunar "month"?
I graphed data for the azimuth of moon rises using data from the Griffith Observatory (http://www.griffithobs.org/skyfiles/skymoonrise2012.html).
The period of my graph is about 27.5 days. This is not a match for any of the lunar "months" identified on Wikki. Can anyone help?
I believe what you are observing is related to the moon's movement relative to the background stars which repeats in a time period called a sidereal month. A sidereal month encompasses 27.3 days. Check out http://www.opencourse.info/astronomy/introduction/04.motion_moon/
and search articles on the sidereal month.