NGC6779 (M56)
 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)=    19.867 +-  0.104
 a(1)=     2.216 +-  0.162
 a(2)=     0.342 +-  0.150
 a(3)=     0.078 +-  0.134
Power-of-x coeffients a(0)+a(1)x+a(2)x^2+..., where x=1+(r/r_c), r_c=1.43
 a(0)=     7.9808
 a(1)=     1.4630
 a(2)=    -0.2222
 a(3)=     0.2617
log r(arcsec)   mu_V    mu_V(fitted)  residual   weight  data set