7 minutes ago, AK_Aramis said:

A large sil plus several blues for stationary, and maybe even a free upgrade... it's almost impossible to miss a planet, and hitting a large target on a planet should also be almost automatic.

You'd think that'd be the case, but you're targeting a relatively small area on a larger area from a long distance away, which means that small changes in angle result in large changes in lateral movement.

A 1 degree shift in the gun angle results in a 1.7% shift in the lateral aim point of the gun. At 10m, 1.7% means you've moved the aim point 17mm to one side, or slightly more than the width of some ammo. At 200km that same 1 degree shift means you've moved the lateral aim point by 3.5km which is way more than the size of this building.

Just now, Kallabecca said:

You'd think that'd be the case, but you're targeting a relatively small area on a larger area from a long distance away, which means that small changes in angle result in large changes in lateral movement.

A 1 degree shift in the gun angle results in a 1.7% shift in the lateral aim point of the gun. At 10m, 1.7% means you've moved the aim point 17mm to one side, or slightly more than the width of some ammo. At 200km that same 1 degree shift means you've moved the lateral aim point by 3.5km which is way more than the size of this building.

Modern fire control accuracy is 0° 0' 2.58" of arc accuracy to over 1.6 km. (2 cm target moving 1000km/h at 1.6 km PUBLISHED accuracy of the CIWS, throwing 10mm autocannon and accounting for drop and wind...)

Hitting a 20m diameter dome doing 0 is MUCH much easier.

The issue isn't "Can we hit it?"
the issue is "Can we hit it just right so we damage it?"

8 minutes ago, AK_Aramis said:

Modern fire control accuracy is 0° 0' 2.58" of arc accuracy to over 1.6 km. (2 cm target moving 1000km/h at 1.6 km PUBLISHED accuracy of the CIWS, throwing 10mm autocannon and accounting for drop and wind...)

Hitting a 20m diameter dome doing 0 is MUCH much easier.

The issue isn't "Can we hit it?"
the issue is "Can we hit it just right so we damage it?"

Except that Star Wars is more akin to WWII technology. They don't use radar guided, computer controlled fire control systems to bring the guns to bear. They have crews of people manning the weapons and directing their fire.

53 minutes ago, Kallabecca said:

Except that Star Wars is more akin to WWII technology. They don't use radar guided, computer controlled fire control systems to bring the guns to bear. They have crews of people manning the weapons and directing their fire.

As seen in Rebels when they actually manage to miss the shield dome over a rebel base with orbital bombardment.
Though it is rebels, so everything has to be taken with a grain of salt, the same orbital bombardment showed extremely low powered turbolasers at this range.

3 hours ago, Kallabecca said:

Except that Star Wars is more akin to WWII technology. They don't use radar guided, computer controlled fire control systems to bring the guns to bear. They have crews of people manning the weapons and directing their fire.

Funny, but most of the projectile-based weapons are guided missiles. If you miss, they get a chance to hit.

Likewise, we know that the targeting computer is pretty good... it's more whether tha gunner reacts in time.

For targeting purposes, I'd probably consider it Silhouette 4; the power supply is hidden and the external dome is big, but not nearly capital-ship-sized (Sil 5+). It's worth noting that the emplacement could be deployed in other configurations - there's nothing that I know of saying that the power supply has to buried a kilometer down into the ice or substrate of your choosing.

Those measures, coupled with the on-station Gonk droids and technicians, would give it a healthy amount of System Strain. I'd figure that the Defense would be pretty high if it's made to withstand return fire from invading capital ships, and could be even higher with a shield like the Rebel base on Hoth. With high Defense, you could get away with low-to-moderate Hull Threshold to simulate the delicacy of some of the components, I suppose.

An emplacement like this is fairly expensive, vanishingly rare, and labor-intensive to install, operate, and maintain. The Rebellion didn't have one (that we know of) on Yavin, so the one on Hoth might have been the only one they owned! With that in mind, I wouldn't mind giving it some pretty ridiculous stats. The wisdom of allowing a party of PCs to acquire/own/operate one is a topic for another thread, I think.