  Differential atmospheric refraction (DAR) limits the amount of light that can
be coupled into a single mode fiber and provides additional complications for
any fiber tracking system. We present an atmospheric dispersion corrector (ADC)
design based off of two counter-rotating prisms to fit the needs of exoplanet
spectroscopy for the Keck Planet Imager and Characterizer (KPIC) from 1.1 to
4.2 microns. Due to strong telluric effects, we find that the default Zemax
prescription for DAR between 2 and 4.2 microns to be inaccurate up to 15 mas
when comparing against DAR models computed from first principles. Using
first-principle models, we developed our own custom ADC optimization solution
and achieve less than 4 mas residual dispersion in any individual science band
(J, K, L) down to 60 degree zenith angles, while the whole time maintaining
less than 3 mas of residual dispersion in the tracking band (H) and less than 2
mas of residual dispersion between the tracking and science bands.
