So we have the standard diffraction equation for crystals, being: nλ = 2dsinθ. If we keep the wavelength and the lattice parameter the same then n simply depends on θ. So there must be a maximum order diffraction ring that you could obtain as once you get to 90° you're essentially going in the opposite direction with the same angles you've already covered. Intuitively you'd think to just rearrange to find the maximum n as n = (2dsin90°)/ λ or n = 2d/λ. But my question is, would you begin to get weird effects from the "slits" in planes below that would change this result?