NGC6656 (M22)
 8 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)=    20.207 +-  0.165
 a(1)=     3.349 +-  0.263
 a(2)=     0.545 +-  0.177
Power-of-x coeffients a(0)+a(1)x+a(2)x^2+..., where x=1+(r/r_c), r_c=1.98
 a(0)=     7.2998
 a(1)=     0.9048
 a(2)=     0.6535
log r(arcsec)   mu_V    mu_V(fitted)  residual   weight  data set