Illustration of the difference in the orientation of the apsid lines in D_H-function. The “E” stands for ecliptic; O₁ denotes the orbit of the northern branch of the meteoroid stream; O₂ is the orbit of the southern branch of the meteoroid stream; N₁ and N₂ are the ascending and descending nodes of the orbits where meteors have been observed, respectively; P₁ and P₂ denote perihelion points of both orbits; N is the common node of both orbits; π in red denotes the difference in the orientation of the apsid lines of the two orbits as measured from the common node N.