Acts 1:9

while they beheld That they might have as clear proof of His Ascension as they had received of the reality of His Resurrection, He is taken from them while they are still gazing on Him and with His words yet sounding in their ears. In the Gospel (Luke 24:51) it is "while He blessed them." From the narrative in this place the witnesses of the Ascension seem to have been only the eleven, and this is stated expressly in St Mark's Gospel (Mark 16:14), so that although in St Luke's Gospel (Luke 24:33) the two disciples who had returned from Emmaus are related to have come unto the eleven to report what they had seen, we are not to conclude that they remained with them during all the other events recorded in that chapter, an additional evidence that that chapter relates to events which happened in the course of several days and not all in close sequence on the same day. Cp. Acts 1:3, note.