Real Quick: there's an imperial defector being kept hidden on a small planet and posing as a civilian miner. he reports to the rebels gathered information he obtains using contacts still in the empire. The empire gets a mole into the mining outfit after his spying is discovered and soon an Imperial Star Destroyer comes after him. It's up to the party to get him out of there and any miners they can AND discover the mole before the Empire straight up murders everyone.

So the scenario I want is the classic "let's blast off and escape this Star Destroyer into hyperspace." They have to clear the planet and calculate the jump. What ranges are we talking about to make this the most effective chase? I want something scary, but not impossible. What is the distance between a planet surface and "in orbit"? I prefer RAW if possible. Also for a lambda shuttle and 3 or 4 PCs, I'm thinking a # of TIE Fighters equal to their number.

So, breaking this up into three hurdles, the first hurdle will probably be the TIEs. If you have a relatively fresh faced bunch of characters here, or slightly more experienced (100 to 200 xp earned through play) but no one with combat pilot or gunnery related talents, You probably don't want them engaging more than 1 to 2 minion packs of 2 to 4 TIEs at a time. Assuming a stock Lambda class, the TIEs will have a huge advantage in terms of speed and maneuverability, so the only gun that will likely be brought to bear on the TIEs is the Aft retractable twin light blaster cannons. The bad news for that weapon is it has a crit of 4, but the good news, it has linked one, so if a gunner can consistently hit 1S2A, That's one TIE/LN down a turn, possibly more if they can hit 4S2A.

Now with RAW, the sensor range on the Lambda means that anyone on board won't be able to see the TIEs until the TIEs are 1 range band out of weapons range, and an ISD can carry a total of 72 fighters. Now, not all of those will be the TIE/LN, but somewhere near half probably will be, with the remaining TIEs split up between Interceptors, no more than 24 Bombers (probably) and maybe depending on the time frame a handful of other more advanced TIEs like the Defender. Depending on the character skill level, I'd keep the Defenders in the hangar for this one, as the Interceptor will be plenty scary enough if a wave or two of TIE/LNs proves to be a cakewalk.

Now, basing the following on table 7-12 in AoR on page 260, you will see we don't actually have numbers for how long it takes to get from the surface to orbit, but we can infer them. If it takes 30 to 90 minutes to go from the surface of a planet to it's moon, figure it will take maybe 10 to 15 minutes to go from the surface to a low but stable orbit and then another 5 to 15 minutes to get to a safe hyperspace point. This 15 to thirty minute trip will be what I would call the "second hurdle." Your players will basically have two options. Run for it, or stand and fight (which may also be known as suicide). While the Lambda is on it's ascent trajectory, the ISD will probably be relaying telemetry to all of it's fighters it sent out to look for your merry band of rebels. They will be vectoring in (which allows you for near limitless reinforcements as a pack of TIEs goes down to keep the tension up) unless the players think a little outside the box and try and dive into a major storm. While the RAW will provide penalties to all parties flying through a storm, one thing from the common sense department is "A Lambda is somewhat aerodynamically shaped, TIE fighters are not." A storm may buy the group some time to put a little distance and maybe give a technician or a droid a chance to put out some fires. Call it the "Ascent Phase Half Time."

The third and final hurdle will be what is waiting for them after they break atmosphere and are in space. Most systems have common points that people come into or out of hyperspace from. Odds are, the ISD is already in that neighborhood, and probably deploying a picket line of TIEs. Upside, there are now bad guys in front of the Lambda, where it can use it's bigger guns, downside, there are more bad guys. First off, the bad news: Most of the weapons on an ISD will make very short work of a Lambda. The picket line of TIEs however, should actually help mitigate the threat of a wall of turbolasers, as no one wants a friendly fire incident, right? So once they hit space, figure it will take them maybe 5 rounds of flying towards the jump point. Let them mix it up with the ties for about 3 turns, then the TIEs pull back. At this point, ISD gets the last two turns, but remember that the biggest scariest turbolasers on the ISD will only be able to fire once in that time, which is a good thing because about two hits would take a showroom new lambda to just this side of flying scrap metal.

Now, if the group has a dedicated pilot and a dedicated gunner with talents appropriate to increasing the chance of survival, and if someone in the party is mechanic enough to fix the ship in flight, I would consider a full pack of four TIEs at a time, or smaller groups of interceptors during this encounter, or giving the ISD more turns in the final hurdle.

Anyway, hope this helps!

I figure it makes perfect sense for the Empire to send TIE fighters in first to soften them up. I could easily keep these numbers to as low as three or four fighters or at most 2 groups of 2-3. I don't want the TIE fighters to chop them up too badly. I just want them to jostle them and provide a bit of sport. I really really don't want those long knives of the ISD to get more than 2 shots off.

as far as the starting range is concerned; I like putting the safe distance for hyperspace at at least long range from the planet surface. The ISD should be something like extreme range away and, naturally, it should be right in the way or close enough to provide distress to an astrogation check. The players can either try to sink it while under heavy fire or outrun the ISD so they can get into the clear. The way that sets things up is that TIE fighters going first means they can get there and mix it up before the ISD's long knives logically can; sweeping the atmosphere for the rebels to cut off their escape. I might put them at short range as soon as the party saddles up.

So essentially it goes like this: Close range (atmosphere: nothing going on), short range (atmosphere/orbit: TIE Fighters), medium range (orbit: nothing), long range (orbit/deep space: nearest safe hyperspace point), extreme (deep space: star destroyer)

In regards to the sensor ranges listed in the books, IMO they're beyond absurd, and apparently I'm reading them right.

I understand (and respect!) that you're trying to use the RAW to handle the situation, but this happens to be a situation where the RAW are $#!t. I don't have a great answer on how to fix them, but I would simply ignore what's in the book and go with what works best for your story. Try to be consistent, but narrative comes first.

You might just want to call it a chase scene from the very beginning with a set number of rounds that equate to, roughly, how long it takes for them to reach the hyperspace jump point.

Say, 5-6 rounds of chase scene. Start with TIEs chasing them from atmo. Round 3-4 they detect the Star Destroyer and it gets in on the chase. Then on the last round have them roll the Astrogation check, failure and they have to try next round, threats give the Imps boosts or the PCs setbacks, and Despair adds an additional round.