The feast of the Ascension of the LORD is a Double of the First Class with a privileged Octave of the third order.
The celebration of the feast began yesterday afternoon with first Vespers. The antiphons Viri Galilaei etc were sung with Psalms 109, 110, 111, 112 & 116. The Office hymn at Vespers, for the feast and Octave, is Salutis humanae Sator. Its final verse is never changed. At Compline Te lucis is sung to the tone of the Ascension Doxology Jesu tibi sit gloria, Qui victor in caelum redis, Cum Patre et almo Spiritu, In sempiterna saecula.
At Mattins the invitatory is proper: Alleluia, Christum Dominum ascendentem in caelum, Venite adoremus, alleluia. The Office hymn is Aeterne Rex altissime. In the first nocturn the antiphons Elevata est etc are sung with Psalms 8, 10 & 18. The lessons are taken from the Incipit of the Acts of the Apostles. In the second nocturn the antiphons Exaltare Domine etc are sung with Psalms 20, 29 & 46. A sermon of St. Leo on the Ascension provides the lessons. In the third nocturn the antiphons Nimis exaltatus est etc are sung with Psalms 9, 98 & 10, the homily is from St. Gregory. At Lauds the antiphons Viri Galilaei etc are sung with the Dominical psalms. The Office hymn is Salutis humane Sator.
At the Hours Sunday psalms are sung, Prime is as on feasts (Pss. 53, 118(i) & 118(ii). At Prime the verse Qui scandis super sidera is sung in the short responsory today and until the Vigil of Pentecost. Hymns (with the exception of Salutis humane Sator) have the Ascension Doxology and are sung in tone 4.
At Mass the Gloria is sung. After the Gospel the Paschal Candle is extinguished. The Credo is sung and the preface and communicantes are proper to the feast. After Mass the Paschal Candle is removed from the sanctuary, it makes a brief re-appearance on the Vigil of Pentecost.
Second Vespers are the same as first except for the antiphon on the Magnificat.
In 'the liturgical books of 1962' the antiphons at the Little Hours are doubled and the Ascension Doxology is sung at the hymn of Mattins only. The hymns at the Little Hours are sung to the general festal tone. The feast's octave was stripped away in 1956.
Icon: Bulgarian 16th century from Wikipedia.