I've successfully made interplanetary transfers (manually to Duna, MechJeb has gotten me to Eve and Duna as well), and I think I'm doing it the hard way. My normal SOP lately is to put a protractor (mod) on my ship, then wait until protractor says my launch window is up. I park in a 75km orbit, then wait for the angles, and make my burn (which is usually around 1050 m/s). This pretty much never gets me an intercept, though. It doesn't even really get me very close. I play around with maneuver nodes, can't nail down an intercept, and then tell MechJeb to tune my approach. MechJeb then wants to make a 400-500m/s burn to fix my approach. From everything I've read, this combined total of ~1500m/s dV is much more than I should be spending to get into a Duna intercept. Also, I've tried using Kerbal Alarm Clock to wait for transfer windows (both modes, which don't agree), and it doesn't agree with Protractor on when transfer windows are, and none of them agree with MechJeb on when transfer windows are. What is it I'm doing wrong, here, and, for my own curiosity, how "wide" are the transfer windows? If I attempt a transfer a few days to either side, how much does that hurt me in terms of required dV? I'm sure these questions come up all the time, but I wasn't able to find any succinct answers, so I appreciate any help the collective wisdom could provide.