AAVSO SPP Program

The AAVSO SPP program includes a number of RR Lyrae stars and a few delta Scutid stars with large amplitudes, although data on any short period pulsating star can be submitted to the AAVSO International Database.  These stars typically have a small range, often less than one magnitude, so CCD observations are preferred over visual ones.  CCD observations should be through a standard filter to allow data sets to be merged together, and to minimize the effects due to the color changes these stars undergo during the pulsation cycle.  Many Cepheid stars are quite bright and photometry with a digital SLR or even a webcam is practical.  Refer to the AAVSO DSLR Observing Manual for more information.

RR Lyrae Ephemeris

Each year the AAVSO SPP Section issues a month-by-month prediction of times of maximum (ToMx) for selected RR Lyrae and large-amplitude delta Scuti stars.  This document lists times when each star will be at its maximum brightness.  (Hint:  to save these to your local system right-click and choose "Save link as")

RR Lyrae Ephemeris 2024
RR Lyrae Ephemeris 2023
RR Lyrae Ephemeris 2022
RR Lyrae Ephemeris 2021
RR Lyrae Ephemeris 2020
RR Lyrae Ephemeris 2019
RR Lyrae Ephemeris 2018
RR Lyrae Ephemeris 2017
RR Lyrae Ephemeris 2016
RR Lyrae Ephemeris 2015
RR Lyrae Ephemeris 2014
RR Lyrae Ephemeris 2013


RR Lyrae Ephemeris Generator

In addition to the PDF ephemeris above, an online ephemeris generator for RR Lyrae and delta Scuti stars is available.  This site allows the user to input their location and select a magnitude range, and generates a nightly list of stars that can be observed at the selected site.

Program Stars

The Table 1 lists some RR Lyrae stars that exhibit the Blahzko effect as well as some large-amplitude delta Scuti stars that have multiple periods. These stars should be observed several times every few seasons, at all phases (not just during maximum) to look for changes in the primary and Blazhko periods. The light curves for the multi-periodic delta Scuti stars are complex and vary markedly from cycle to cycle.  The RR Lyrae and delta Scuti stars in Table 2 appear to have single, stable periods without any Blazhko effect.  These need "time of maximum" (ToMx) measurements every few years to check for any changes in period that may occur. 

Table 1 - Legacy stars with a Blazhko effect
For these stars, multiple lightcurves at all phases, observed in a single season can be used to check the Blazhko period. This only needs to be done every few years to check for changes in both the fundamental and Blazhko periods.

Note: because the behavior of AC And and VX Hya are so irregular, these stars do not appear in the AAVSO Ephemeris.

Table 2 - Legacy stars with no Blazhko effect
Stars that only require observation  once each year or two to check for changes in the fundamental period.

Table 3 - Legacy Cepheid Stars
These legacy Cepheid stars were taken from Tom Cragg’s  committee reports from 50+ years ago along with a few stars added by Horace Smith and Gerry Samolyk.

Table 4 - Other Target Cepheids
This table contains some other interesting Cepheids compiled by Dave Hurdis when the SPP section was formed.