Several people have pointed out that the disc of the Sun rests on the shoulder of Virgo rather than over her midsection.  This is evidence, they say, that the woman is not clothed with Sun.  As far as the astronomical alignment is concerned, this is the only point that can withstand any scrutiny, but it doesn't ultimately hold water for several reasons:

First, from the perspective of an earth-based observer, the Sun itself is significantly smaller than the constellation Virgo and so regardless of where the Sun is positioned, the woman could never be fully clothed with the Sun if the disc itself is in view in Revelation 12:1.  Even if the disc rested over Virgo's midsection, it would only cover a small portion of her torso.  On September 23rd, 2017, the Sun clothes the woman's shoulder, which in my opinion is just as significant as any other part of her body.  You can see the vast difference in apparent size between the constellation Virgo and the Sun below, and why its location within the constellation makes no difference:

Second, the Greek word for "Sun" in Revelation 12:10 is ἥλιον, transliterated hēlion, which is Strong's 2246 - hélios.  The word can carry several meanings: the Sun, the rays of the sun, sunlight, and daylight.  Ancient Greek didn't have different words for these four meanings as we do in English, so hélios carries other connotations beyond just the literal meaning of "Sun".  The use of the word in the Septuagint with its definite article in 2 Samuel 12:11 is perhaps a good example of this where the idea is "broad daylight" - τοῦ ἡλίου.  The Revelation 12 Sign not only appears in its fullness over Israel during the day on September 23rd, but because the Sun is in the area of the constellation, the woman appears fully "clothed" in the Sun's rays.

Third, and lastly, arguing that the disc of the Sun doesn't "clothe" the woman is an impossible standard.  Virgo is the only constellation in the biblical Mazzaroth that represents a woman and out of 88 constellations in the sky, one of only three that represent women.  Of those three, it is the only one that the Sun moves through - hence Virgo being part of the Mazzaroth - the twelve constellations that lie along the Sun's ecliptic.  For this reason, if John's vision was of a literal sign in the sky (which the text in Revelation 12:1 plainly says it was), Virgo is the only possible constellation in the entire sky that could symbolize the woman.  The Sun's ecliptic is exactly the same every year and the only time the Sun ever enters the torso of Virgo is when it passes just behind the angle formed by Spica as seen below:

The image above shows the deepest possible point in the constellation that the Sun traverses (the red line is the Sun's unchanging path every year).  The Sun will never hover over Virgo's neck or chest, or be centered anywhere in the quadrangle of the constellation's womb, nor will it ever cover her legs, so "clothed with the Sun" must simply mean that the Sun is passing through the constellation as it does every Fall for a little over one and a half months.  You can test this yourself using any astronomy software - whether you choose 3000 BC or 3000 AD makes no difference.  It is interesting to note that if you bisect Virgo into two equal parts, the Sun's position on September 23rd, 2017 is about as close as the Sun ever gets to being perfectly centered over the constellation.  "Clothed in the Sun" probably also draws on the connotations mentioned in the second point above, which is that the woman is clothed in sunlight or the rays of the Sun.

In September 2017 we see a perfect match with John's prophecy.

Many watchers are making the connection between the Revelation 12 Sign and the rapture based on the male child's possible corporate identity as the Body of Christ - the Church.  A number of detractors dismiss this possibility, but in my opinion the evidence is simply too powerful to ignore and even if the astronomical alignment on September 23rd is not the Revelation 12 Sign, I would still argue that the man-child in Revelation 12:5 is meant to represent the Church in union with Christ.  Here are the reasons:

First, it is repeated ad infinitum by detractors that the Church is the bride of Christ and thus the man-child cannot represent the Church.  This is a very exegetically weak argument for several reasons.

For starters, the Church is called a man in Ephesians 2:15.  There are a number of metaphors for the Church in Scripture besides a bride.  The most common is actually Christ's body (e.g. 1 Corinthians 10:16-17, 12:12-13, 25-27; Romans 12:4-5; Colossians 1:18, 24, 2:19, 3:15; Ephesians 4:4, 11-13).  And what might come as a shock to some, the Church is never explicitly identified as the bride of Christ.  The closest you can come to that analogy is in 2 Corinthians 11:2 and Ephesians 5:22-24.  In the Ephesians passage the Church is likened to a bride in that that the Church is subject to Christ who is the head, but the Church is not said to actually be the bride.  The only explicit reference to Christ's bride is found in Revelation 21:2, 9-10.  The bride is the city of New Jerusalem, which is revealed after the millennial reign of Christ.  New Jerusalem has characteristics from both Israel and the Church, with gates named after the sons of Jacob (men who died long before Christ's first advent), and foundations named after the Twelve Apostles.  Zion, which is a prophetic term for heavenly Jerusalem, is likened to a woman in labor in Isaiah 66:8, so in a certain sense it is really Zion, the mother of all the saints both pre- and post-Christ, that is the wife of the Lamb.  We need to remember that bride is just one analogy of many for the Church, just as body is.  The Church is just as often compared to a temple (1 Corinthians 3:16-17, 6:19; 2 Corinthians 6:16; Ephesians 2:19-22; 1 Peter 2:5).

Second, the Apostle John makes a grammatical error in Revelation 12:5 when he modifies the masculine huios (son) with the neuter word arsen.  If you believe that God's Word is infallible, then you're only left with one option: John made this mistake intentionally.  And sure enough, his use of arsen appears to come directly from the Septuagint version of Isaiah 66:7-8 where we see the same imagery of a woman in labor with a male child.  Isaiah 66:8 gives the male child an unmistakable corporate identity - he is a nation born in a single day.  1 Peter 2:9 says the Church is a holy nation.

Third, Revelation 12:5 says that the male child "will rule all the nations with an iron scepter".  This is an important clue.  There is no question that this phrase relates to Christ as can be seen in Psalm 2:9 and Revelation 19:14-15.  However, Revelation 2:26-27 unmistakably gives the promise to "rule with an iron scepter" to the Church, as well.  There is no way to get around verse 27 - Christ, in union with His Church, will rule the nations with a rod of iron.

Fourth, the corporate identity of the male child preserves the symbolic pattern of Revelation 12: the woman is Mary and Israel, the dragon is satan and his kingdom, and the child is Christ and His Church.

Fifth, the use of harpazó in Revelation 12:5 is a huge clue.  Harpazó is the same word used for "rapture" or "caught up" in 1 Thessalonians 4:17 and means a sudden removal by force.  Jesus' ascension was never once described using this word and in fact the Apostle John himself (the author of Revelation) calls Jesus' ascension anabainó in John 20:17 - meaning to go up, ascend, or rise.  When Jesus ascended to Heaven He had already conquered death and sin.  He was in absolutely no danger from anyone.  The Bible says He left not to escape satan, but because it was beneficial for the Church (John 16:7).  There is simply no way to reconcile the context of Revelation 12:5, which is a sudden snatching away by force from the imminent danger of the dragon, with Jesus' ascension.

Sixth, Revelation 12 is significantly placed right in the middle of the book and is an interlude presenting a broad overview of Christ's first coming all the way up to the end of the Tribulation: Christ's birth, the gestation and birth of the Church, the war in Heaven, the rise of antichrist's kingdom (seven heads and ten horns), Israel being pursued by the dragon during the first-half of the Tribulation (Revelation 12:13), Israel being miraculously protected by God for the last-half of the Tribulation (Revelation 12:14), and even satan's pursuit of the Tribulation Saints once he realizes he can't touch the divinely protected Jews (Revelation 12:17).

Seventh, I firmly believe that the early Church was dispensational, premillennial, and pretribulational.  However, with the rise of Augustinianism, the Church went through a 1,400-year hiatus where prophecy tended to be mistrusted and allegorized.  The founders of modern dispensationalism who re-popularized the pre-trib rapture such as Darby and Ironside found Revelation 12:5 to actually be the chief proof-text of the pretribulational rapture of the Church.  By the early 1900s, this proof-text was largely forgotten by pre-trib proponents and arguments in favor relied primarily on secondary evidence, which led to the rise of mid-trib, pre-wrath, and post-trib views in the Evangelical churches.  I find it fascinating that around the same time the Revelation 12 Sign was first spotted using astronomy software (sometime in 2011 or 2012), a number of scholars, such as Michael Svigel, re-discovered the use of Revelation 12:5 as the chief pre-trib proof-text.  The timing is impeccable.