2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/222539We present the first results of an observational project, which addresses the period changing behaviour of a sample of high-amplitude delta Scuti stars. In this paper we discuss the double-mode nature of V567 Ophiuchi. It was observed on 15 nights in two consecutive years in order to resolve the long-standing ambiguity related to its secondary period. A frequency analysis of almost 5000 individual single-filtered CCD V measurements resulted in two independent frequencies (f_1=6.6879 c/d and f_2=11.8266 c/d) with a ratio of f_1/f_2=0.565. Earlier data taken from the literature were used to refine the dominant period, and the re-analysis supports the existence of the secondary period. Possible asteroseismological implications are briefly discussed.6 pages, 3 figures, to appear in A&A, references correctedAstrophysicstext