Did a little googling
Time to decelerate to zero:
time=(speed/deceleration)
For example if current speed is 900 and deceleration 300px/s, then you need 3 seconds to stop the ship.
Formula to calculate the distance:
Distance=deceleration*(time^2)/2
So to stop at target you need to start deceleration at distance 300*9/2=1350px