QUESTION: How could shifting the viewpoint northward make a missile heading to the right switch to heading left?
ONLY ANSWER: The aircraft was heading eastward all the time.
Yeah, I know ;-)
I'm an engineer at a military test range. I design instrumentation systems that track flying targets (mostly short and medium range missiles). We think about these kinds of geometric problems every day. Unlike the average joe, we aren't fooled by foreshortening and parallax effects. I know this stuff forwards and backwards.