nt=n_elements(t)
kM=t
dt=t
for it=0,nt-1 do begin
  dt(it)=t(it)-t0+.5
  kM(it)=total(spec2(1:*,it))/total(spec2(1:*,it)/k(1:*))
endfor
plot_oo,dt,kM
oplot,38./dt^.6667,col=122
END