Personally, I interpret "constellations" to just be a fancy way of organizing perks and to have nothing to do with stars in the sky. :shrug:

Why would the thirteen birthsigns directly tie to skills?

Doesn't make sense to me and I don't think that's how it's done in Skyrim.

Please direct your attention to page 55 of the GI article. In the bottom right is the screen showing Conjuration, Destruction, and Restoration constellations as well as parts of the Illusion and Restoration constellations. The constellations which are related to the skills are not the birth signs, so there is no discrepancy. Also I have not read everything lore related but I would guess that since these constellations are minor in comparison to the birth signs they are rarely discussed.

Actually if you look at the screenshot in the game informer article the constellation's for the magic skills appear to be *inside* the mage. That is to say it is possible the magical skills are lesser charges of the mage. Just as The Apprentice, The Atronach, and The Ritual are what you would call his major charges. Honestly, I think they are doing this because it looks cool and they will explain it in the lore inside the game.

Edit* also, read the post above me. They are not birth signs if that what you people are getting at.

Well taking in account this [censored] thing of constelation= skill, since we humans have much more skills in our day to day than damn birthsign, we have only 3 solutions:
Dragonborns are morons and that would explain why they can only make words of 3 runes. In such case Skyrim is only a delusionary dream from a collective of really mindly challenged people, or people who thinks we are all extremely mind challenged and so they can throw any rat [censored] at us to gobble; (and many customers will do so in girly jumps of joy)
They gonna [censored] lore and comon sense more times than a pedofile is [censored] when he gets in a comon prison cell in Brazil.
They gonna scratch that stupid and pathetic crap, saying its a f(piiii)g hoax. (Henceforth doing the right thing)

Each skill is an *asterism* of the birthsigns constellation? With 18 skills in 3 birthsigns, that's 6 asterisms in each birthsign constellation.
Just for ref, the big dipper (aka plough) is an asterism within the constellation Ursa Major. Northern Cross within Cygnus.
Not sure how they are going to pull off 6 distinct asterisms for 3 birthsigns though.

The article said that the different constellations for every skill are split up into different areas of the sky based on whether they're magic, stealth, a fighting skills. so all the magic skills will be in the magic area of the sky, not inside the mage constellation.

im sure thoes constelations differ from the birthsigns

I'm fairly certain that the 18 skills will be spread across the three major archetypal constellations (The Thief, The Warrior, The Mage). Six skills will be found amongst the stars of each, possibly even being unequally spread across the four signs that the archetypal signs each govern.
That's the only way I can think of it.
I don't think they would just add random signs....