ENR CTIO Blanco 4-m 2022-04-17

The focus changed significantly when moving between targets separated by more than several degrees, and at larger zenith distances, it was often difficult to identify a well-defined optimal value for the focus because none of the tested focus values would produce well-behaved, symmetric PSFs, and because within a given image the focus would seem to vary across the image; some stars would appear well-focused while others were clearly poorly focused.