▁catalog ▁of ▁ 2 , 7 1 2 ▁rich ▁clusters ▁of ▁galaxies , ▁"... a ▁sem inal ▁contribution ▁to ▁observ ational ▁cosm ology ". ▁ ▁The ▁recognition ▁of ▁second ▁order ▁clusters ▁of ▁the ▁clusters ▁of ▁galaxies , ▁which ▁also ▁dis pro ved ▁Carl ▁Char lier ' s ▁hier arch ical ▁model . ▁ ▁The ▁study ▁of ▁lum inos ity ▁of ▁clusters ▁showing ▁how ▁they ▁can ▁be ▁used ▁for ▁determ ination ▁of ▁relative ▁distances . ▁ ▁A ▁list ▁of ▁ 8 6 ▁planet ary ▁ne b ula e ▁which ▁includes ▁Ab ell ▁ 3 9 . ▁ ▁Rec ogn ition ▁that ▁planet ary ▁ne b ula e ▁derive ▁from ▁red ▁giant ▁stars , ▁together ▁with ▁Peter ▁Gold reich , ▁of ▁U CLA , ▁ ▁With ▁Robert ▁G . ▁Harr ington ▁discovered ▁periodic ▁com et ▁ 5 2 P / H arr ington - Ab ell . ▁ ▁An ▁extended ▁version ▁of ▁the ▁clusters ▁of ▁galaxies ▁catalog ue ▁was ▁published ▁after ▁Ab ell ' s ▁death ▁in ▁ 1 9 8 7 ▁under ▁the ▁author ship ▁of ▁Ab ell , ▁Harold ▁G . ▁Cor win ▁and ▁Ron ald ▁P . ▁O low in . ▁ ▁This ▁extended ▁ ▁catalog ▁includes ▁clusters ▁seen ▁from ▁the ▁southern ▁hem is phere , ▁lists ▁approximately ▁ 4 , 0 0 0 ▁clusters ▁of ▁galaxies ▁and ▁includes ▁thirty ▁members ▁with ▁a ▁red shift ▁up ▁to ▁z ▁= ▁ 0 . 2 . ▁ ▁( See ▁List ▁of ▁Ab ell ▁clusters .) ▁ ▁Te aching ▁ ▁U CLA ▁Ab ell ▁taught