The former treatise have I made, O Theophilus, of all that Jesus began both to do and teach, Until the day in which He was taken up, after that He through the Holy Ghost had given commandments unto the apostles whom he had chosen: to whom also He shewed Himself alive after His passion by many infallible proofs, being seen of them forty days, and speaking of the things pertaining to the kingdom of God: and, being assembled together with them, commanded them that they should not depart from Jerusalem, but wait for the promise of the Father, which, saith He, "Ye have heard of me. For John truly baptized with water; but ye shall be baptized with the Holy Ghost not many days hence." When they therefore were come together, they asked of Him, saying, "Lord, wilt Thou at this time restore again the kingdom to Israel?" And He said unto them, "It is not for you to know the times or the seasons, which the Father hath put in His own power. But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth." And when he had spoken these things, while they beheld, He was taken up; and a cloud received Him out of their sight. And while they looked stedfastly toward heaven as He went up, behold, two men stood by them in white apparel; which also said, "Ye men of Galilee, why stand ye gazing up into heaven? This same Jesus, which is taken up from you into heaven, shall so come in like manner as ye have seen Him go into heaven." Then returned they unto Jerusalem from the mount called Olivet, which is from Jerusalem a sabbath day's journey. And when they were come in, they went up into an upper room, where abode both Peter, and James, and John, and Andrew, Philip, and Thomas, Bartholomew, and Matthew, James the son of Alphaeus, and Simon Zelotes, and Judas the brother of James. These all continued with one accord in prayer and supplication, with the women, and Mary the mother of Jesus, and with his brethren. (Acts 1:1-14)
"The feast of the Ascension is the feast of salvation consummated. The whole process of salvation: birth, passion, death and resurrection are completed in the Ascension. "When Thou hadst fulfilled for us Thy dispensation, and united the things in earth with the things in Heaven, Thou, O Christ our God, didst ascend into glory, in no wise being parted from those that love Thee, but Thou didst remain with them inseparably and proclaim to them: I am with you, no one is against you." As an expression of the meaning of this festival, the theme of the Ascension used to be placed in the dome of ancient churches, thus completing the scheme of paintings they contained." (The Meaning of Ikons, p 194)
The Feast of the Ascension of Christ took place, according to scriptural testimony forty days after His resurrection. The timing is significant, as the number "forty" is not only a semitic idiom for "a long time" it refers to significant turning points in the sacred history of Christians and Jews. Moses was on Mount Sinai for forty days, the Hebrews wandered in the desert for forty years, Jesus was in the wilderness for forty days after His baptism. All of these events refer not merely to a space of time, but to the time at which the promises of God were fulfilled. It is the point at which time is "filled up" with the promise of God. So, the Ascension of our Lord occurred at that point in which all that God had promised concerning His Anointed One had not merely come true but had become the focal point and fulcrum of history. The history of the world to that point had been concluded. Christ had appeared to His followers; He had conversed with them - giving them His final teaching; He broke bread with them - revealing Himself as present at the sacred liturgy; He bestowed His peace on them; and He promised them the Holy Spirit - the Comforter who would be in the Church until the end of time. In all of these actions Jesus completed His Incarnation. Godµs presence in the world complete, He ascended in glory not simply as God but as God who had taken human nature. Thus our very humanity is taken to the throne of heaven.
All of this is reflected in the ikon of the feast. The central axis of the ikon is the straight line which can be drawn between the figure of the Mother of God below and the the figure of Christ above. He "Who, being in the form of God, thought it not robbery to be equal with God: but made Himself of no reputation, and took upon Him the form of a servant, and was made in the likeness of men: and being found in fashion as a man, He humbled Himself, and became obedient unto death, even the death of the cross. Wherefore God also hath highly exalted him, and given him a name which is above every name: that at the name of Jesus every knee should bow, of things in heaven, and things in earth, and things under the earth..." (Phil 2:6-10) The second person of the Holy Trinity who became a human being and voluntarily suffered the consequences of human sinfulness now takes that renewed, redeemed, and transfigured human nature to the throne of God. Below, He leaves not a mere collection of people, but the Church - the ekklesia (trans. Hebrew Qahal) the people who are "called out" to be His people and as His Body continue His incarnation, His presence in this world. This ikon is traditionally located in the apse or the ceiling over the altar (it is thought that the arrangement of the Pantokrator in the dome of the Church and the Virgin of the Sign in the apse are an evolution of the ikon of the Ascension which took place as Churches got larger). Christ is shown "Leaving" in the same way in which He will come again at the end of time - surrounded by the Glory of Heaven. Thus the mandorla is not a kind of "heavenly elevator" but a sign of the Divine Light breaking through into this world.
The Ikon shown here is in the ceiling over the altar of SS Peter & Paul Church in Meriden, CT. It was painted by Ivan Diky in 1961-3.