So, if you have a pilot and a copilot, who takes astrogation checks? Also, who controls weapons?

Lewis

The rule of thumb I use for any given ship is:

The pilot can control all functions of the ship unless additional crew members are listed for those functions.

Co-pilots and droid sockets give the ship a second station that has all the same functions as the pilot seat, it just can't take piloting actions in the same round as the pilot and makes co-pilot checks instead.

Ships that have any crew/passenger capacity have at least some additional computer/coms stations on board that allow other characters than the pilot to make checks like astrogation, sensor scans or social checks over coms.

Ships that are so large that they don't list specific stations have a full bridge with numerous redundant stations, character have to move between stations to control this ship if they don't have a large crew.

Moving between stations on the bridge / in the cockpit of a ship takes one maneuver. Moving between stations that are positioned around the ship takes half the ships silhouette in maneuvers.

Anyone can, it depends on the needs of the story.

edit:

im probably a little more liberal than Aetrion, but basically what he said. I will allow a "pilot" and a "copilot" to perform 1 vehicle only Manoeuvre each (in silhouette 4 or smaller vehicles) in the same turn. Just so long as the vehicle itself doesn't exceed its maximum.

i also let shooting be done by anyone with any gun, assuming they can get to the controls. But in the pilot/copilot situation I would allow either to shoot using the forward facing weapons. A turret will require a Manoeuvre to engage with to use on a smaller ship while the bridge of a bigger ship has a station to engage with for gun control. Again the limit of each weapon system only firing once per round is my main limitation I stick to.

Well, it's rule of thumb, not word of god. You just sort of roll with whatever fits the ship ultimately. Getting to the engine room of a Sil 5 or 6 ship can be a whole adventure in itself if it needs to be.