Of course the astronomy matters, but the gaggle of interpretative possibilities is precisely what tells us it *could* have been any of them. How, then, should we choose? My money’s on the triple convergence in 7 BC, but I didn’t pick that one because I liked its interpretative scenario better than other ones. I settled on the triple convergence only after I was convinced that a lot of significant historical data strongly suggests a census and birth in 7 BC. Without building arguments in this post, here are the key points of that data:
If the historical data was more in favor of another year I’d have no problem changing my pick on the "star”, but we have to start with history. Herod’s deathday is the movst vital issue, though I’ve made the case that Archelaus’ exile is actually the best starting point. From those two points, the most important task is to identify specific evidence for the contextual details of a Roman-Herodian census. Historically speaking, the question of how, when and why hundreds or thousands of Roman soldiers were mobilized in Herod’s territory is infinitely more significant than the question of what esoteric particulars inspired the mobilization of a few wealthy, knowledge obsessed individuals.
1) Herod the Great died after an eclipse on a festival day, Purim, in 4 BC
2) Tertullian cited Saturninus as the census taker at Christ's birth
3) Saturninus was Governor of Syria from 9 to 6 BC
4) Herod got in major trouble with Augustus late in 9 BC
5) Event planning for the bizarre logistics of this unusual census must have required significant lead time with advance notification given for local scheduling
6) This special registration did not evaluate property (unlike in 6 AD)
7) Joseph’s fear of Archelaus in 4 BC was irrational, centered on protecting Jesus, and thus unlikely to abate while the Ethnarch was in Judea
8) Any birth date between April 7 BC and March 6 BC makes Jesus 12 at the first Passover after Archelaus was exiled, 7 AD, allowing Joseph to feel safe taking Jesus into Jerusalem
Note: From these points we may conclude that Caesar must have told Saturninus to count Herod’s people, but not to value their property. To preserve the integrity of scripture, we must then also conclude that Luke 2:1 refers to Augustus' provincial registration decree in 27 BC; and that Luke 2:2 should be translated, “this was the census before [the one in which] Quirinius was governor”; and finally that Luke 2:3 refers only to this unique and isolated event, as opposed to all Roman censuses since 27 BC. (See Hoehner and Finegan for more on the greek text of Luke 2:2.)
In short, if we get the history right, the proper “star” should present itself. So this year, my Christmas Wish is that well meaning amateurs (and certain scholars) would spend less time going on about astronomy & astrology, and work a bit harder to learn classical history & geography. On these issues, we definitely need all the help we can get!