NGC6440
 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)=    20.287 +-  0.171
 a(1)=     3.870 +-  0.242
 a(2)=     0.575 +-  0.232
Power-of-x coeffients a(0)+a(1)x+a(2)x^2+..., where x=1+(r/r_c), r_c=0.92
 a(0)=     6.8482
 a(1)=     0.9913
 a(2)=     0.4590
log r(arcsec)   mu_V    mu_V(fitted)  residual   weight  data set