Called All Hallow's Eve or Ancestor Night, it is when the veil between the two worlds is most pervious. 
            Observance begins at sundown on October 31. 

            This third and last of the three pagan Autumn harvest festivals acknowledges a time of cleansing and preparation for the darkness of Winter.  It is the most important of the four "greater Sabbats."  

  Callanish, Lewis, Scotland
“Then I turned and saw in the spaces
of the night sky constellations appear,
one by one, over roof‑tops and houses,
and Cassiopeia trapped: stabbed where
her thigh met her groin and her hand
her glittering wrist, with the pinpoint of a star.”
Eavan Boland

Cassiopeia  - seen at her clearest in early November