As they were looking (blepontōn autōn). Genitive absolute. The present participle accents the fact that they were looking directly at Jesus.
He was taken up (epe4rthe4). First aorist passive indicative of epairō, old and common verb meaning to lift up. In Luk 24:51 we have “he was borne up” (anephereto) and in Act 1:2, Act 1:11; 1Ti 3:6 “was received up” (anelēmpthē).
Received (hupelaben). Second aorist active indicative of hupolambanō, literally here “took under him.” He seemed to be supported by the cloud. “In glory” Paul adds in 1Ti 3:16.
Out of their sight (apo tōn ophthalmōn autōn). From their eyes (apo with ablative case).