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Modern observatories and instruments require optics fabricated at largersizes with more stringent performance requirements. The Daniel K. Inouye SolarTelescope will be the world's largest solar telescope at 4.0 m aperturedelivering a 300 Watt beam and a 5 arc-minute field. Spatial variation ofretardance is a limitation to calibration of the full field. Three polarimetersoperate seven cameras simultaneously in narrow bandpasses from 380 nm to 1800nm. The DKIST polarization calibration optics must be 120 mm in diameter atGregorian focus to pass the beam and operate under high heat load, UV flux andenvironmental variability. Similar constraints apply to the instrumentmodulators with large beams near focal planes at F/18 to F/62. We assess howdesign factors can produce more spatial and spectral errors simulatingelliptical retardance caused by polishing errors. We measure over 5deg circularretardance and spectral oscillations over +-2 for optics specified as strictlylinear retarders. Spatial variations on scales larger than 10 mm contain 90% ofthe variation. Different designs can be a factor of 2 more sensitive topolishing errors with dissimilar spatial distributions even when usingidentical retardance bias values and materials. The calibration for the on axisbeam is not impacted once circular retardance is included. Calibration of thefull field is limited by spatial retardance variation unless techniques accountfor this variation. We show calibration retarder variation at amplitudes of1deg retardance for field angles greater than roughly one arc minute for bothquartz and MgF_2 retarders at visible wavelengths with significant variationbetween the three DKIST calibration retarders. We present polishing error mapsto inform new calibration techniques attempting to deliver absolute accuracy ofsystem calibration below effective cross-talk levels of 1deg retardance.

Polarization Modeling and Predictions for DKIST Part 4: Calibration  Accuracy Over Field of View, Retardance Spatial Uniformity And Achromat  Design Sensitivity