Palomar 4
 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)=     2.199 +-  0.487
 a(1)=     2.888 +-  0.755
 a(2)=     0.577 +-  0.614
Power-of-x coeffients a(0)+a(1)x+a(2)x^2+..., where x=1+(r/r_c)^2, r_c=1.51
 a(0)=    -1.2637
 a(1)=     0.3820
 a(2)=     1.6849
log r(arcsec)   mu_V    mu_V(fitted)  residual   weight  data set