It's a bit iffy with Mars right there.
However, it's an easy fix (especially if you have a quicksave in earth orbit):
If you look at my ship in that screenshot, it's pointing along Earth's orbital path around the sun, plus
a little bit outwards.
Once you've established the direction you need to burn in, simply timewarp until you reach the appropriate spot in your LEO orbit and start burning from there.
If you did it right, your exit trajectory should look like this.
You might not need to angle as much outwards as me, I was doing a very slow burn and you will likely be a faster burn.