LCO image of the Einstein Cross (Q2237+0305) in the R band in inverted grey scale (north is down, east is right and the field size is ~12.4 arcmin × 4.2 arcmin). Overlayed as blue arrows are the proper motions µ_i of stars in the field from Gaia DR3 data (as reference: the high eastward proper motion star on the top right has µ ≈ 55.4 mas yr⁻¹) that we use to improve the image alignment with ISIS (see Sect. 3.1). The PSF star is marked. In the lower right, a zoom into the central part of the image (~25.3 arcsec × l3.6 arcsec), where the Einstein Cross is situated, is shown (image names A–D are indicated). Here we use the reference image for difference imaging in the R band.