▁reached . ▁ ▁When ▁the ▁sun ▁is ▁located ▁at ▁the ▁z en ith , ▁the ▁band ▁of ▁maximal ▁polar ization ▁wra ps ▁around ▁the ▁horizon . ▁Light ▁from ▁the ▁sky ▁is ▁polar ized ▁hor izont ally ▁along ▁the ▁horizon . ▁ ▁During ▁tw il ight ▁at ▁either ▁the ▁V ernal ▁or ▁Aut umn al ▁equ ino x , ▁the ▁band ▁of ▁maximal ▁polar ization ▁is ▁defined ▁by ▁the ▁North - Z en ith - S outh ▁plane , ▁or ▁mer id ian . ▁In ▁particular , ▁the ▁polar ization ▁is ▁vertical ▁at ▁the ▁horizon ▁in ▁the ▁North ▁and ▁South , ▁where ▁the ▁mer id ian ▁meets ▁the ▁horizon . ▁The ▁polar ization ▁at ▁tw il ight ▁at ▁an ▁equ ino x ▁is ▁represented ▁by ▁the ▁figure ▁to ▁the ▁right . ▁The ▁red ▁band ▁represents ▁the ▁circle ▁in ▁the ▁North - Z en ith - S outh ▁plane ▁where ▁the ▁sky ▁is ▁highly ▁polar ized . ▁The ▁cardinal ▁directions ▁N , ▁E , ▁S , ▁W ▁are ▁shown ▁at ▁ 1 2 - o ' clock , ▁ 9 ▁o ' clock , ▁ 6 ▁o ' clock ▁and ▁ 3 ▁o ' clock ▁( counter - clock wise ▁around ▁the ▁cel est ial ▁sphere ▁since ▁the ▁observer ▁is ▁looking ▁up ▁at ▁the ▁sky ). ▁ ▁Note ▁that ▁because ▁the ▁polar ization ▁pattern ▁is ▁dependent ▁on ▁the ▁sun , ▁it ▁changes ▁not ▁only ▁throughout ▁the ▁day ▁but ▁throughout ▁the ▁year . ▁ ▁When ▁the ▁sun ▁sets ▁toward ▁the ▁South , ▁in ▁the ▁winter ,