NGC6715 (M54)
 9 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)=    19.631 +-  0.116
 a(1)=     5.648 +-  0.196
 a(2)=     0.598 +-  0.159
 a(3)=    -0.168 +-  0.122
Power-of-x coeffients a(0)+a(1)x+a(2)x^2+..., where x=1+(r/r_c), r_c=0.85
 a(0)=     4.9317
 a(1)=     0.8174
 a(2)=     0.7186
 a(3)=    -0.0710
log r(arcsec)   mu_V    mu_V(fitted)  residual   weight