slit	Ratio	error
-1	18.64	0.4
-2	18.18	0.38
-3	20.85	0.5
-4	18.15	0.34
-5	17.44	0.31
-6	17.38	0.32
-7	17.82	0.32
-8	16.41	0.27
-9	18.51	0.37