NGC6539       c
 6 iterations.
Chebyshev coeffients a(0)T_0(u)+a(1)T_1(u)+..., where u is log (r/arcsec) mapped to [-1,1]
 a(0)=    21.822 +-  0.165
 a(1)=     3.963 +-  0.307
 a(2)=     1.565 +-  0.217
 a(3)=     0.464 +-  0.196
Power-of-x coeffients a(0)+a(1)x+a(2)x^2+..., where x=r
 a(0)=     8.4300
 a(1)=     0.5890
 a(2)=    -0.3320
 a(3)=     0.4577
log r(arcsec)   mu_V    mu_V(fitted)  residual   weight  data set