▁rotation ▁also ▁means ▁that ▁the ▁time ▁of ▁year ▁the ▁Sun ▁is ▁in ▁a ▁given ▁const ell ation ▁has ▁changed ▁since ▁Bab yl onian ▁times . ▁ ▁Because ▁the ▁division ▁was ▁made ▁into ▁equal ▁ar cs , ▁ 3 0 ° ▁each , ▁they ▁constit uted ▁an ▁ideal ▁system ▁of ▁reference ▁for ▁making ▁predictions ▁about ▁a ▁planet ' s ▁longitude . ▁However , ▁Bab yl onian ▁techniques ▁of ▁observ ational ▁measurements ▁were ▁in ▁a ▁rud iment ary ▁stage ▁of ▁evolution . ▁They ▁measured ▁the ▁position ▁of ▁a ▁planet ▁in ▁reference ▁to ▁a ▁set ▁of ▁" normal ▁stars " ▁close ▁to ▁the ▁e cli ptic ▁( ± 9 ° ▁of ▁latitude ) ▁as ▁observ ational ▁reference ▁points ▁to ▁help ▁position ing ▁a ▁planet ▁within ▁this ▁e cli ptic ▁coordinate ▁system . ▁ ▁In ▁Bab yl onian ▁astronom ical ▁di aries , ▁a ▁planet ▁position ▁was ▁generally ▁given ▁with ▁respect ▁to ▁a ▁z odia cal ▁sign ▁alone , ▁less ▁often ▁in ▁specific ▁degrees ▁within ▁a ▁sign . ▁When ▁the ▁degrees ▁of ▁longitude ▁were ▁given , ▁they ▁were ▁expressed ▁with ▁reference ▁to ▁the ▁ 3 0 ° ▁of ▁the ▁z odia cal ▁sign , ▁i . e ., ▁not ▁with ▁a ▁reference ▁to ▁the ▁continuous ▁ 3 6 0 ° ▁e cli ptic . ▁In ▁astronom ical ▁e ph emer ides , ▁the ▁positions ▁of ▁significant ▁astronom ical ▁phen omena ▁were ▁computed ▁in ▁sex ages imal ▁fra ctions ▁of ▁a ▁degree ▁( equ ivalent ▁to ▁minutes ▁and ▁seconds ▁of ▁arc ). ▁For ▁daily ▁e ph emer ides