inkychris

I have done the calculations for this. Essentially you want to leave at 180 degrees from where the target (eg. KSC) is going to be after the time it takes to Hohmann transfer between the low Kerbin orbit and the geostationary orbit. Both by calculation and simply placing a node (mechjeb helps) the time taken from node to geostationary can be found. I used a 100km orbit to start and the time was 1h 23m, so you want to calculate the angle Kerbin has rotated in that time. Kerbin period is 6h so 360/6=60. 60x(1+23/60)=83 so the KSC will have rotated 83 degrees since you left your node and have reached geostationary. Since you want to leave 180 degrees from where KSC will end up, we want to leave 97 degrees behind KSC. This will mean the probe position will have rotated 180 degrees in 1h 23m, when KSC has done 83 degrees, the 2 line up and you simply circularise. Job's a gooden. If like me you are using mechjeb and the coordinates, make sure to be aware that as you rotate counter-clockwise (at low Kerbin orbit), when above the KSC your west value will be 74, it will reduce down to 0, then back up to 180 and back down again. Without knowing this I was burning at the 'wrong' 170 degree mark, so if you use 100km orbit, warp past KSC then to 170 upwards, then past 180 it will come back down to 170, this is when you burn. If you want angles then add and subtract from this point. With the angles, mechjeb is useful as you can bring up surface info coordinates and leave at 170 degrees west (KSC is at 74) but if you didn't have that you could use time based methods, which again after some calculation I found with a 100km orbit to be leaving 523 seconds which is 8m 43s. You need to be careful with this though as if you place a node above KSC then warp to t- 8:43, the KSC will have rotated and you'll need to readjust accordingly until you're happy with the margin of error. I might have a go at the time based method when setting a node with the probe above KSC then calculating the error and a true departure time but that would just be effort...