NGC6316
 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)=    20.052 +-  0.131
 a(1)=     2.996 +-  0.210
 a(2)=     0.338 +-  0.170
Power-of-x coeffients a(0)+a(1)x+a(2)x^2+..., where x=1+(r/r_c), r_c=1.11
 a(0)=     7.3660
 a(1)=     1.2204
 a(2)=     0.3750
log r(arcsec)   mu_V    mu_V(fitted)  residual   weight  data set