  The Habitable zone Planet Finder (HPF) is a fiber fed precise radial velocity
spectrograph at the 10 m Hobby Eberly Telescope (HET). Due to its fixed
altitude design, the HET pupil changes appreciably across a track, leading to
significant changes of the fiber far-field illumination. HPF's fiber scrambler
is designed to suppress the impact of these illumination changes on the radial
velocities -- but the residual impact on the radial velocity measurements has
yet to be probed on sky. We use GJ 411, a bright early type (M2) M dwarf to
probe the effects of far-field input trends due to these pupil variations on
HPF radial velocities (RVs). These large changes ($\sim$ 2x) in pupil area and
centroid present a harsh test of HPF's far-field scrambling. Our results show
that the RVs are effectively decoupled from these extreme far-field input
changes due to pupil centroid offsets, attesting to the effectiveness of the
scrambler design. This experiment allows us to test the impact of these changes
with large pupil variation on-sky, something we would not easily be able to do
at a conventional optical telescope. While the pupil and illumination changes
expected at these other telescopes are small, scaling from our results enables
us to estimate and bound these effects, and show that they are controllable
even for the new and next generation of RV instruments in their quest to beat
down instrumental noise sources towards the goal of a few cm/s.
