Prograde and Retrograde change when a target is selected

[RocketBlam]

It's all in the title. Why does this happen? If I have a target selected (as in, trying to intercept it), then if I turn to "prograde" and burn, it doesn't actually point at prograde. Somehow, it has set a new "prograde" for my ship, one that is not actually prograde. If I unselect the target, the real prograde marker shows up again and I can point to it. But it gets really tiresome to, for example, have to deselect a target, point to normal or anti-normal, and then re-select it to adjust your orbit so it lines up with the target. In fact, I don't think the normal and anti-normal markers even show up when you have a target selected.

What sense does this make? What is it supposed to accomplish? Or is it just a bug?

[FullMetalMachinist]

Click on the velocity indicator, it'll cycle between surface, orbital, and target modes, with the markers changing for each one (though usually the surface and orbital ones will be really close). 

[FancyMouse]

It is supposed to help you do the rendezvous, especially the last couple of km. "Pushing the target retrograde marker towards anti-target" is the usual trick to get you like 10m near your target from several km distance, ready to dock.

And as said above, if you want the usual orbital prograde/retrograde, click the "Target" text right above the velocity number. Cycle it to "Orbital" and you'll be happy.

[cubinator]

The navball shows your velocity relative to the target when in target mode. If you were to burn retrograde to 0 m/s you'd be stationary relative to the target. Click on the velocity indicator to set the navball relative to the parent body again.

Edited July 19, 2016 by cubinator
Stupid autocorrect

[klesh]

One is a prograde maker in reference to your orbit around a planet and the other is in reference to the target's position, hence the change.  Not a bug. 

[IWanttobeEVA]

When you're in 'target' mode the nav-ball indicators relate to you're vessel's velocity vector relative to the target. If the prograde indicator lines up with the target indictor it means you're approaching the target head on. You use these in target mode to match your orbit and position to the target vessel. 

[Red Iron Crown]

Gameplay question moved to Gameplay Questions.

As others have mentioned, target mode on the navball sets the frame of reference to one centered on the target, which is incredibly handy for matching speed when performing rendezvous or during docking maneuvers. Click the speed readout to change the frame of reference to orbital or surface as required.

[RocketBlam]

1 hour ago, klesh said:

One is a prograde maker in reference to your orbit around a planet and the other is in reference to the target's position, hence the change.  Not a bug. 

I see. Thanks for the answers.

Don't we already have a "target" and "anti-target" marker in the navball, though? What's the difference with how it works now?

[Red Iron Crown]

3 minutes ago, RocketBlam said:

Don't we already have a "target" and "anti-target" marker in the navball, though? What's the difference with how it works now?

Target points directly at the target, anti-target directly away from it, in any reference frame. Prograde in the target frame of reference is your direction of movement in relation to the target, which may or may not be directly toward it. If you adjust your prograde marker to match the target marker then you are headed directly for it.

[bewing]

 

There is a difference between direction and velocity, and you have to have the difference very very clear in your head for these words to actually make sense.

Target/anti-target show direction from your nose to the target. Prograde/Retrograde show your movement (with respect to the target). So you can be looking straight at the target, but moving totally sideways to it.

When you are doing a rendezvous, as said above, you want to kill your movement. So you burn retrograde in target mode, until your target velocity goes to 0. It doesn't matter which direction the actual target is -- what you want to kill is the movement itself. Once the movement has gone to zero, then you point the nose at the target and do a little burn. Suddenly the target prograde marker will appear, showing you that you are moving in the new direction that you burned.

Edited July 19, 2016 by bewing

[RocketBlam]

So it's essentially a manual way to do MechJeb's "Match Target Velocity"?

[Red Iron Crown]

5 hours ago, RocketBlam said:

So it's essentially a manual way to do MechJeb's "Match Target Velocity"?

That's probably the most common use for it. Set up a rendezvous, then when you're at the point of closest approach switch to target mode, point retrograde and thrust until speed is 0m/s.