angles = [-90, 0, 90]
pulse_widths = [595, 1480, 2440]

>>> import numpy
>>> numpy.polyfit(angles, pulse_widths, 2)
array([4.62962963e-03, 9.41666667e+00, 5.95000000e+02])

pulse_width = 4.62962963e-03 * angle ** 2 + 9.41666667 * angle + 595

pw = (pulse_widths[0] * (angle - angles[1]) * (angle - angles[2])) / ((angles[0] - angles[1]) * (angles[0] - angles[2])) +
    (pulse_widths[1] * (angle - angles[0]) * (angle - angles[2])) / ((angles[1] - angles[0]) * (angles[1] - angles[2])) +
    (pulse_widths[2] * (angle - angles[0]) * (angle - angles[1])) / ((angles[2] - angles[0]) * (angles[2] - angles[1]))