!# $N$ filter from Koo (1986), ApJ 311, 651.
"NK"
"energy"       
"Vega"    0.
 6800.   0.000
 6900.   0.128
 7000.   0.396
 7100.   0.639
 7200.   0.811
 7300.   0.885
 7400.   0.936
 7500.   0.972
 7600.   0.989
 7700.   0.999
 7800.   1.000
 7900.   0.992
 8000.   0.977
 8100.   0.966
 8200.   0.950
 8300.   0.929
 8400.   0.902
 8500.   0.870
 8600.   0.843
 8700.   0.749
 8800.   0.567
 8900.   0.339
 9000.   0.179
 9100.   0.084
 9200.   0.027
 9300.   0.008
 9400.   0.000
