  We report small angle neutron scattering of the skyrmion lattice in MnSi
using an experimental set-up that minimizes the effects of demagnetizing fields
and double scattering. Under these conditions the skyrmion lattice displays
resolution-limited Gaussian rocking scans that correspond to a magnetic
correlation length in excess of several hundred {\mu}m. This is consistent with
exceptionally well-defined long-range order. We further establish the existence
of higher-order scattering, discriminating parasitic double-scattering with
Renninger scans. The field and temperature dependence of the higher-order
scattering arises from an interference effect. It is characteristic for the
long-range crystalline nature of the skyrmion lattice as shown by simple mean
field calculations.
