code: def XYZ_to_galcencyl(X,Y,Z,Xsun=1.,Zsun=0.,_extra_rot=True):
      
      XYZ= nu.atleast_2d(XYZ_to_galcenrect(X,Y,Z,Xsun=Xsun,Zsun=Zsun,
                                           _extra_rot=_extra_rot))
      return nu.array(rect_to_cyl(XYZ[:,0],XYZ[:,1],XYZ[:,2])).T
docs: NAME:
  
         XYZ_to_galcencyl
  
      PURPOSE:
  
         transform XYZ coordinates (wrt Sun) to cylindrical Galactocentric coordinates
  
      INPUT:
  
         X - X
  
         Y - Y
  
         Z - Z
  
         Xsun - cylindrical distance to the GC
         
         Zsun - Sun's height above the midplane
  
         _extra_rot= (True) if True, perform an extra tiny rotation to align the Galactocentric coordinate frame with astropy's definition
  
      OUTPUT:
  
         R,phi,z
  
      HISTORY:
  
         2010-09-24 - Written - Bovy (NYU)