An angel of the Lord appeared to him, standing on the right side of the altar of incense.
The right hand side ... This was the north side of the altar; and the inclusion of such details indicates that Luke's research had extended far enough to discover such circumstantial knowledge as this.  Scholars have been quick to point out that in this section the precise, elegant Greek preface (Luke 1:1-4) has been replaced by a style of language steeped in the traditions, religion, and psychological attitude of the Hebrews, a style which it would have been impossible for any man to improvise, showing how carefully Luke had researched these events.  Some have tried to explain this by supposing "that St. Luke is here using a Hebrew document";[14] but such a supposition is sheer unadulterated imagination.  As is also evident, later in the chapter, and with regard to Mary, "The psychological detail Luke gives indicates he may have INTERVIEWED Mary, as later passages will confirm."[15]  Of course, the same is true here.