NGC6366
 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)=    23.010 +-  0.228
 a(1)=     2.231 +-  0.343
 a(2)=     0.515 +-  0.321
 a(3)=     0.162 +-  0.300
Power-of-x coeffients a(0)+a(1)x+a(2)x^2+..., where x=1+(r/r_c), r_c=2.12
 a(0)=     9.6274
 a(1)=     1.8672
 a(2)=    -1.2006
 a(3)=     0.9791
log r(arcsec)   mu_V    mu_V(fitted)  residual   weight  data set