Participants of the project: leader V.I.Burnashev, B.A.Burnasheva, V.G.Shitov in cooperation with Russian investigators E.A.Vitrichenko, Space Sciences Institute; N.A.Gorynia, N.N.Samus, M.E.Sachkov, Institute Astronomy

INTRODUCTION
The RV Tau-type stars form a small group of about 200 stars among other types of variables.

RV Tau-type variables are old, low-mass, yellow supergigant pulsating variable stars whose light curves show alternaty deep and shallow minima. Some RV Tau (RVb) show long secondary periods: their mean magnitudes vary with periods of 600 - 1500 days, the other (RVa) - do not vary in mean magnitudes.

The scarce of the RV Tau-stars may be the evidence that these variables are post AGB stars, a rather transident phase whith occupies only a few thousand years.

The photometric investigation of RV Tau stars has begun near 100 years ago, but up to date the photoelectric observations are carried out for a few stars only.

The cause of the alternativy deep and shallow minima is not clear and that of the long-term variation in mean magnitude and periods is unknown.

SPECIFIC GOAL OF PROJECT
Since up to date the photoelectric observations are scarce, and are carried out for a few stars, there is worth-while to undertake the photometric investigation of RV-Tau- stars by means of CCD-photometer, attached on the telescopes of Crimean astrophysical observatory.

The analysis of our data and the published one might to shed light on the long-period variations of those stars, the simultaneous photometric and radial- velocity measurments might be used for the determinations of their radii.

THE LAST RELEVANT PUBLICATIONS OF THE PROJECT PARTICIPANTS
V.I.Burnashev, B.A.Burnasheva, E.A.Vitrichenko. CCD-photometry of the RV-Tau stars. I. TT Ophiuchi. Bull.Crimean astrophys.obs., v.98, p.123, 2002.

V.I.Burnashev, B.A.Burnasheva, N.A.Gorynia, N.N.Samus, M.E.Sachkov. CCD- photometry of the RV-Tau stars. II. AC HERCULIS. Bull.Crimean astrophys. obs. (submitted).

V.I.Burnashev, B.A.Burnasheva, E.O.Waagen. CCD-photometry of the RV-Tau stars. III. V VULPECULAE. Bull.Crimean astrophys.obs. (submitted).

V.I.Burnashev, B.A.Burnasheva, E.O.Waagen. CCD-photometry of the RV-Tau stars. IV. R SAGITTAE. Bull.Crimean astrophys.obs. (submitted).