That would suggest with the naked eye you could look at the moon and pick out features about 20km wide https://skyandtelescope.org/observing/how-to-see-lunar-c

That would suggest with the naked eye you could look at the moon and pick out features about 20km wide https://skyandtelescope.org/observing/how-to-see-lunar-craters-with-the-naked-eye102820152810/ https://skyandtelescope.org/observing/how-to-see-lunar-crate... "At 0.8′ (arcminutes) across, the crater alone hovers at the naked-eye limit" Which seems to back the the c. 1/60th idea. Judging the resolution of an eye is a subjective process, not least beacuse of the relative sensititivty and density of rods and cones at different parts of the eye.