TypeRVA (RV Tauri type)Click for lightcurveThese are radially pulsating supergiants having spectral types F-G at maximum light and K-M at minimum. The light curves are characterized by the presence of double waves with alternating primary and secondary minima that can vary in depth so that primary minima may become secondary and vice versa. The complete light amplitude may reach 3-4 magnitudes in V. Periods between two adjacent primary minima (usually called formal periods) lie in the range 30-150 days (these are the periods appearing in the Catalogue). Two subtypes, RVA and RVB, are recognized. RVA do not vary in mean magnitude.AAVSO Alert Notice 529 October 1, 2015Observing campaign on 5 variables in CygnusDr. George Wallerstein (University of Washington) has requested AAVSO assistance in monitoring 5 variable stars in Cygnus now through December 2015. He is working to complete the radial velocity curves for these stars, and needs optical light curves for correlation with the spectra he will be obtaining.Dr. Wallerstein writes: "I need to know the time of max or min so I can assign a phase to each spectrum. Most classical cepheids are quite regular so once a time of max or min can be established I can derive the phase of each observation even if my obs are several cycles away from the established max or min. MZ Cyg is a type II cepheid and they are less regular than their type I cousins." SZ Cyg, X Cyg, VX Cyg, and TX Cyg are all classical Cepheids.V and visual observations are requested. These are long-period Cepheids, so nightly observations are sufficient; many observations made over one night are not necessary.