See Acts 1:12. When Jesus ascended, he did so from the Mount of Olives near Jerusalem. There were about 120 followers of Christ in Jerusalem at the time of the Ascension (Acts 1:15) but if you compare Acts 1:11-13, it would appear that only the 11 Apostles were present at the Ascension of the Lord. I say this because the Angel addressed them as "Men of Galilee" in verse 11 and then in verse 13, the 11 are named. Remember that Judas Iscariot, who betrayed the Lord had not yet been replaced.
I hope you have found this helpful.