Equations for the elevated horizon were derived using spherical trigonometry
by Mark Takken, a 10th grader in 2020 at North Salem Schools, NY.


Define the angles
l     latitude
e    elevation above geometric horizon
x    right ascension in deg
y    declination.

Then

y(x,e,l) = 90 - a + b,    if x < 90 or x > 270
             = 90 - a - b,    if  90 ≤ x ≤ 270

with
a = arccos[sin(e)/cos(h)]
b = arccos[sin(l)/cos(h)]
h = arcsin[sin(x)cos(l)]

This is graphed at desmos.com/calculator/vtgikoccnz
For further information contact Mark

June, 2020