How to launch into a specific inclination

[xcorps]

How do you figure your heading for a launch into a specific inclination?

For instance, I had a NKO asteroid I wanted to capture with an inclination of 42. I had a grabber rocket ready to go with over 12k Dv, but launching 90 then circ'ing orbit then changing inclination then trying to plot a hohmann transfer didn't work. Closest I could get was 139k and all the maneuvers to intercept involved expending an unreasonable amount of Dv because my relative approach speed was way too damn high.

I think I could have done the capture if I could have launched into the right inclination and then just set peri right behind the asteroid then adjusted speed as I came around as it was only moving like 456m/s.

[cantab]

Launch when either KSC or its antipode is directly under the asteroid's projected path. A marker such as a flag at KSC helps you see it on the map, and adjusting the camera so the asteroid's path appears directly behind the centre of Kerbin helps you line things up. When you do your gravity turn, aim slightly west of the desired inclination (to compensate for Kerbin's rotation), and make sure you're not heading retrograde compared to the asteroid! During your ascent switch to map view, open the navball, and aim slightly west or east of your prograde vectore to fine-tune your inclination as you build up speed. Just watch your resources panel if you do this before you're on your final stage.

[xcorps]

Thank you cantab.