Panel a: historical LC of V426 Sge from 1900 to the present as given by our photographic m_pg/m_pv magnitudes (blue/green triangles), ASASSN and our V magnitudes (red triangles). Gray triangles with arrows denote a limiting magnitude on plates with unseen target. Panel b: detail of the LC covering the 1968 symbiotic nova outburst. Decline from the maximum and wave-like periodic variation are denoted by the dotted and full line, respectively. Panel c: V-LC from 2015 to the present showing the ASASSN and our data. Panel d: UBVR_CI_C LCs covering the 2018 outburst and the present quiescence. Vertical bars and crosses denote the dates of our low (L) and high (H) resolution spectra. Dotted vertical lines in panels c and d mark the light minima according to the ephemeris (1).