NGC6426
 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)=    22.752 +-  0.237
 a(1)=     2.791 +-  0.411
 a(2)=     0.476 +-  0.321
 a(3)=     0.348 +-  0.216
Power-of-x coeffients a(0)+a(1)x+a(2)x^2+..., where x=1+(r/r_c), r_c=1.33
 a(0)=     8.7108
 a(1)=     3.3494
 a(2)=    -2.2362
 a(3)=     0.8039
log r(arcsec)   mu_V    mu_V(fitted)  residual   weight  data set