Terzan 7
 3 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)=     0.935 +-  0.166
 a(1)=     1.496 +-  0.246
 a(2)=     0.395 +-  0.225
 a(3)=    -0.283 +-  0.206
Power-of-x coeffients a(0)+a(1)x+a(2)x^2+..., where x=1+(r/r_c)^2, r_c=1.35
 a(0)=    -0.3454
 a(1)=    -3.0631
 a(2)=     5.6114
 a(3)=    -1.7529
log r(arcsec)   mu_V    mu_V(fitted)  residual   weight  data set