Mechanical stability of a microscope setup working at a few kelvins for single-molecule localization

► Localization precision of the image of a point source is free from diffraction. ► Prerequisite for the precision is stability of the sample and objective at 1.5 K. ► We developed a rigid imaging unit to make image of scattering of a sample bead. ► The centroid of the scattering image of a bead was determined for 800 images. ► The standard deviation of the 800 centroids measured in 17 min was 0.85 nm.