6 0 ), ▁ ▁at ▁University ▁College ▁London ▁( 1 9 6 0 - 1 9 6 2 ), ▁lect urer ▁( 1 9 6 2 - 1 9 7 0 ) ▁and ▁ ▁senior ▁lect urer ▁( 1 9 7 0 - 1 9 9 9 ). ▁He ▁was ▁assistant ▁director ▁of ▁the ▁University ▁of ▁London ▁Observ atory ▁( 1 9 6 6 - 1 9 8 9 ) ▁and ▁subsequently ▁became ▁Director ▁from ▁ 1 9 8 9 ▁to ▁ 1 9 9 7 . ▁ ▁He ▁was ▁Chair man ▁of ▁the ▁International ▁Astronom ical ▁Union ▁Working ▁Group ▁on ▁Ad verse ▁Environment al ▁Imp act s ▁on ▁Astronom y ▁( 1 9 9 7 - 2 0 0 0 ). ▁He ▁was ▁visit ing ▁fellow ▁at ▁the ▁University ▁of ▁H ert ford shire ▁since ▁ 1 9 9 9 . ▁He ▁became ▁Chair man ▁of ▁the ▁International ▁Council ▁of ▁Scient ific ▁Un ions ▁Working ▁Group ▁on ▁Ad verse ▁Environment al ▁Imp act s ▁on ▁Astronom y ▁from ▁ 1 9 9 3 ▁till ▁ 1 9 9 7 . ▁ ▁He ▁was ▁Secretary ▁of ▁the ▁Royal ▁Astronom ical ▁Society ▁( 1 9 6 6 - 1 9 7 1 ), ▁then ▁Vice ▁President ▁( 1 9 7 1 - 1 9 7 2 ) ▁and ▁Tre as urer ▁in ▁ 1 9 9 6 . ▁ ▁He ▁was ▁the ▁Ass istant ▁General ▁Secretary ▁of ▁the ▁International ▁Astronom ical ▁Union ▁from ▁ 1 9 8 5 ▁to ▁ 1 9 8 8