Remove constraints on detector_pixel that it should be an integer from 0 to npix. Since these values correspond to SIAF aperture 'sci' coords and only get converted to 'tel' (V2/V3), there's no reason to constrain to the detector focal plane, especially since it is possible to simulate PSFs outside this region via SI WFE extrapolation. Also, fractional values are necessary to track small shifts (e.g., coronagrahic masks) and provide sub-pixel coordinate transformations.

Explicitly set x,y=map() in order to force map to return the values, otherwise it gets saved as an object, and we are unable to subscript the values as expected.