Hi Alan,
I wish I could help you and respond to your question. As it stands now, I know practically nothing about T20
Part of the issue here is nailing down what exactly is Navigation? For example...
Marc Miller clearly states that accuracy of jump is +/- 3,000 km per parsec jumped. I can't get my mind around what precisely this means because of the variable of TIME. If Time is variable, then where exactly is the jumpspace +/- error margin supposed to apply to? Planets move. If you aim for a planet and miss it by a day - you miss it by more than a mere 3,000 km! If you miss it by as much as 20 minutes (1 turn in Classic traveller) - you'd miss EARTH by as much as 20,000 miles! Clearly, this is more than the 3,000 km spoken of by Marc.
So where does that leave us? That 3,000 Km has to be based on some specific frame of reference. Is it the star's frame of reference? Is it some absolute frame of reference such as the center of the universe? If you miss by as little as 1 second, the sun will have moved a set number of miles (as suns move at a rate of miles per second!)
For me, and for a play by email game I will run eventually - frame of reference refers to the primary sun. This way, if you miss by an hour, and you hoped to intercept Earth - then you will either be 1 hour ahead of earth or 1 hour behind earth depending how badly off you were in your navigation roll. So, the question you have to ask yourself is this: "Is it good to get out of jump space early?" SURE! If you can make up the distance between you and the world you wanted to end up in - in less than a day's journey. Is it ok to be a day late? Well, not really - because now you have to race to catch up to a fleeing object so to speak. You have to build up momentum, catch up to it, and slow down...
Frankly? The better the navigation roll, the closer you are to your intended temporal (time) exit point. The worse your navigation roll, the worse your timing will be. The question that hits most wargames is simpley this: "If I missed, did I miss short or did I miss long"
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