NGC6205 (M13)
 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)=    21.463 +-  0.100
 a(1)=     6.095 +-  0.153
 a(2)=     1.403 +-  0.169
Power-of-x coeffients a(0)+a(1)x+a(2)x^2+..., where x=1+(r/r_c)^2, r_c=1.65
 a(0)=     6.0358
 a(1)=     0.2500
 a(2)=     0.9054
log r(arcsec)   mu_V    mu_V(fitted)  residual   weight  data set