Goodness-of-fit χ² plane for the pole scan for (1917) Cuyo with a constant rotation period. For a 5° × 5° grid of possible pole positions, in ecliptic longitude λ and latitude β, the shape model and sidereal rotation period were optimised. Goodness-of-fit χ² values foreach model were recorded. They are colour coded, with darker colours marking the lower χ² values and anything above twice the minimum value of χ² is white. Thewhite contour line indicates a 10% increase relative to the minimum χ² value obtained (marked with a “+”) and the black contour line is a 50% increase. The fragment of the celestial sphere was chosen with the smallest χ² values, for a more detailed 1° × 1° scan, as shown in Fig. 3.