subroutine afc65b(cx,cy,npts,nfast,fsample,nflip,ipol,xpol, + ndphi,iloop,a,ccfbest,dtbest) logical xpol complex cx(npts) complex cy(npts) real a(5),deltaa(5) a(1)=0. a(2)=0. a(3)=0. a(4)=45.0*(ipol-1.0) deltaa(1)=2.0 deltaa(2)=2.0 deltaa(3)=2.0 deltaa(4)=22.5 deltaa(5)=0.05 nterms=3 if(xpol) nterms=4 ! Don't fit polarization when solving for dphi if(ndphi.ne.0) nterms=3 ! Start the iteration chisqr=0. chisqr0=1.e6 do iter=1,3 !One iteration is enough? do j=1,nterms chisq1=fchisq(cx,cy,npts,nfast,fsample,nflip,a,ccfmax,dtmax) fn=0. delta=deltaa(j) 10 a(j)=a(j)+delta chisq2=fchisq(cx,cy,npts,nfast,fsample,nflip,a,ccfmax,dtmax) if(chisq2.eq.chisq1) go to 10 if(chisq2.gt.chisq1) then delta=-delta !Reverse direction a(j)=a(j)+delta tmp=chisq1 chisq1=chisq2 chisq2=tmp endif 20 fn=fn+1.0 a(j)=a(j)+delta chisq3=fchisq(cx,cy,npts,nfast,fsample,nflip,a,ccfmax,dtmax) if(chisq3.lt.chisq2) then chisq1=chisq2 chisq2=chisq3 go to 20 endif C Find minimum of parabola defined by last three points delta=delta*(1./(1.+(chisq1-chisq2)/(chisq3-chisq2))+0.5) a(j)=a(j)-delta deltaa(j)=deltaa(j)*fn/3. enddo chisqr=fchisq(cx,cy,npts,nfast,fsample,nflip,a,ccfmax,dtmax) if(chisqr/chisqr0.gt.0.9999) go to 30 chisqr0=chisqr enddo 30 ccfbest=ccfmax * (1378.125/fsample)**2 dtbest=dtmax if(a(4).lt.0.0) a(4)=a(4)+180.0 if(a(4).ge.180.0) a(4)=a(4)-180.0 if(nint(a(4)).eq.180) a(4)=0. ipol=nint(a(4)/45.0) + 1 if(ipol.gt.4) ipol=ipol-4 return end