Originally Posted by LukeS
I imagine that the disparity is so minutely different for
objects 1000m and 2000m away that a shaky finger and a cross
eyed measurement will not accurately bring out the real
distance/disparity, and generally as the curve flattens off as
we measure and collate the splitting for objects further and
further away, it will be increasingly difficult to calculate and
Yep, a quick calculation (using angle rather than distance, because it's
easier) gives a value of 0.463597 at 1000m, 0.463622 at 2000m. That's a
relative difference of about 0.0054 percent. The moon turns out to be
0.463647, another 0.0054 percent away from them by some strange coincidence.
(The formula for the angle I got was
where d is the distance to the object, c is the distance to finger
("calibration") and e is the distance between your nose and an
eye. I assumed c was 0.1 and e 0.05).
Edit: Here's a graph of the angle against distance (in metres):
in principle the method should work, shouldn't it?
Yep, it's called parallax and we do use it to measure nearby stellar objects
(albeit the "eyes" are the Earth on opposite points of its orbit
around the sun).