!# $F$ (<-> $R_F$?) filter from Kron (1980), ApJS 43, 305.
"FK"
"energy"       
"Vega"    0.
 4900.   0.000
 4950.   0.143
 5000.   0.226
 5050.   0.292
 5100.   0.357
 5150.   0.398
 5200.   0.440
 5250.   0.434
 5300.   0.429
 5350.   0.417
 5400.   0.405
 5450.   0.405
 5500.   0.405
 5550.   0.423
 5600.   0.440
 5650.   0.470
 5700.   0.500
 5750.   0.548
 5800.   0.595
 5850.   0.613
 5900.   0.631
 5950.   0.607
 6000.   0.583
 6050.   0.560
 6100.   0.536
 6150.   0.512
 6200.   0.488
 6250.   0.482
 6300.   0.476
 6350.   0.500
 6400.   0.524
 6450.   0.553
 6500.   0.583
 6550.   0.637
 6600.   0.690
 6650.   0.768
 6700.   0.845
 6750.   0.893
 6800.   0.940
 6850.   0.970
 6900.   1.000
 6950.   0.863
 7000.   0.726
 7050.   0.375
 7100.   0.024
 7150.   0.012
 7200.   0.000
