  We compute instanton sizes and study correlation functions between instantons
and monopoles in maximum abelian projection within SU(2) lattice QCD at finite
temperature. We compare several definitions of the topological charge,
different lattice actions and methods of reducing quantum fluctuations. The
average instanton size turns out to be $\sigma \approx 0.2$ fm. The correlation
length between monopoles and instantons is $\zeta \approx 0.25$ fm and hardly
affected by lattice artifacts as dislocations. We visualize several specific
gauge field configurations and show directly that there is an enhanced
probability for finding monopole loops in the vicinity of instantons. This
feature is independent of the topological charge definition used.
