From Fig. , the 3σ measurement accuracy for a 5-s phase measurement is ±0.0024°, which from Eq. ( ) implies a 3σ measurement accuracy of ±0.0024° for the optical rotation angle too. Hence, when the polarimeter is operated at a time resolution of 5-s, fewer than 0.3 % of optical rotation angle measurements will be 'out' by more than 0.0024°. The accuracy reported here is very similar to that obtained using the set-up described in our previous paper, using commercial mounts and a costlier laser and speed controller. To put the accuracy value in context, the Vishnyakov polarimeter was quoted as having a 3σ accuracy of ±0.0014°, while high-resolution commercial polarimeters from leading manufacturers have typical accuracies of ±0.002° (see Supplementary Table ). Hence, despite its low cost, the polarimeter described here is capable of achieving near state-of-the-art resolution.