NGC6304
 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)=    19.683 +-  0.137
 a(1)=     2.720 +-  0.226
 a(2)=     0.232 +-  0.181
Power-of-x coeffients a(0)+a(1)x+a(2)x^2+..., where x=1+(r/r_c)^2, r_c=1.22
 a(0)=     7.3517
 a(1)=     1.3688
 a(2)=     0.2705
log r(arcsec)   mu_V    mu_V(fitted)  residual   weight  data set