As a skill, Astronomy will let you navigate by the stars. There has been mention of skilled Astronomers venturing into the realm of Astrology and revealing the destiny of others.
I had a bit of a discussion with Matrim Cauthon about this and here's some ideas we came up with.
Discovering Talents
While it could be potentially used for finding out if someone has a latent talent and what that talent might be, it's my personal opinion that this should not be included. Talents are a mysterious force that create story twists. If they are made easy to discover then they cease being that special thing and become just another item on the checklist to take care of during your characters lifetime. So leave it out.
Fortune Telling
The use of Fortune Telling would be two-fold.
First, it could provide hints to a characters personal story arch. SBS has mentioned that the Soulborn Engine will create story objectives for each character that will follow the character around and activate when certain conditions are met. By using Fortune Telling, hints could be provided that would lead a character to unlock those conditions.
For example, your character is destined to fight a pteroguin but this is unknown to you. You get your Fortune read and are guided to spend some time in a part of the land that is native to large groups of pteroguin. This way, the Fortune doesn't directly tell you what to do but improves the chance of it happening by focusing your attention in a certain location. Since these story quests are already established, getting a Fortune told would just be pulling a detail from that quest in the form of a hint.
In true Fortune Telling form, you could get a wrong or false reading. This false reading chance would decrease as the Astronomers skill rises. Too many false readings would lead to discouragement and lack of use for the skill so I don't think it should start at any higher than 50% when first made available.
Secondly, you could use Fortune Telling to guide you toward your Soulmate. If your twin soul was not activated yet at the time of the reading then you would simply learn that there is no draw towards another. However, if someone was playing your Soulmate the reading could present a direction that the character is in at that moment. Something like, "follow the tail of Manticore," which would be the star at the end of the constellation of Manticore positioned SW of you. Later on you could get another reading to see if the direction changed. A bit like tracking on a massive scale and using the stars instead of footprints.
Prophecy
Similar to Fortune Telling but involving world-wide events. This would produce results that would not be limited to a single Astronomer, many users across the world would forecast the same thing. An example would be: "A King will fall," when a King hits that black line and has only a short time left before their spirit vanishes and they die of old age. Another example: "A new land will be discovered," when the devs have opened up a new continent and over-sea travel is made available. In fact, the devs could use Prophecy as a way of informing players of new features in-game without coming right out and saying it! How awesome would that be?
I hope this has sparked some ideas of your own and I'd love to know what you think on this subject!