One of my Skype students is practicing the D Major scale in contrary motion. (Her thumbs at Middle D)
We start slow triplets to 16ths, to 32nds (Legato/Staccato/Forte/piano)
The snag occurs at the third and final octave out, where most students think the notes are off the radar–but in truth peripheral vision and/or rolling eyeballs can fool the brain into thinking those notes are ON screen.
Regardless, I prefer that my pupils look straight ahead and “feel” their way along the three octave journey out and back.
For those who need a bit of a crutch, I allow eyes to follow the Left Hand, as the “Right Hand” is felt. Or it can be vice versa.
The best techniques to beef up the so-called elusive octave at the extremes, are to use rhythms (dotted 8th/16th) long-short-long as I demonstrate in the video, and to do some blocking of tunnels. The student can play thumbs together at the last octave (LH going down as RH ascends on D) and block 23 together, as thumbs meet in between, followed by the 234 blocks and a rotational 5 on the final Ds. (All demonstrated in my video instruction)
In any case, this pupil improved her total scale rendering by scoping out the last vulnerable octave. She had also done considerable work on toning up the whole scale.
Our respective segments are included in the you tube posting.