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.

Variable Type Period days) Blazhko (days) Notes
SW And RRab 0.4423 36.8  
AC And RR      Has 2 or 3 periods
RS Boo RRab 0.3773 533  
ST Boo RRab 0.6223 284  
SW Boo RRab 0.5136 13  
TV Boo RRc 0.3126 33.5  
RW Cnc RRab 0.5472 87  
TT Cnc RRab 0.5634 89  
XZ Cyg RRab 0.4666 57.3  
DM Cyg RRab 0.4199 26  
RW Dra RRab 0.4429 41.6  
XZ Dra RRab 0.4765 76  
RR Gem RRab 0.3973 37  
AR Her RRab 0.4700 31.6  
DL Her RRab 0.5916 33.6  
SZ Hya RRd 0.5372 25.8 Dual mode
VX Hya Delta Sct 2 periods   Has a strong beat period between the two periods
RR Lyr RRab 0.5668 39  
RZ Lyr RRab 0.5112 116.7  
RV UMa RRab 0.4681 90.1  

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.

Variable Type Period (days)   Notes
XX And RRab 0.7228    
AT And RRab 0.6169    
SW Aqr RRab 0.4593    
TZ Aur RRab 0.3917    
BH Aur RRab 0.4561    
SZ Boo RRab 0.5228    
TW Boo RRab 0.5323    
UU Boo RRab 0.4569    
UY Boo RRab 0.6510    
RR Cet RRab 0.5530    
TW Her RRab 0.3996    
VX Her RRab 0.4554    
DY Her Delta Sct 0.1486    
UU Hya RRab 0.5239    
DG Hya RRab 0.7542    
DH Hya RRab 0.4890    
RR Leo RRab 0.4524    
SS Leo RRab 0.6263    
TV Leo RRab 0.6729    
WW Leo RRab 0.6029    
SZ Lyn Delta Sct 0.1205   Part of a binary system.
AV Peg RRab 0.3904    


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.

Variable Type Max Min   Period (days)
SZ Aql DCEP 7.92 9.26 V 17.137939
TT Aql DCEP 6.46 7.7 V 13.7546
Eta Aql DCEP 3.48 4.39 V 7.176641
RU Cam CWA 8.1 9.79 V 22
SZ Cas DCEPS 9.6 10.02 V 13.63289
Del Cep DCEP 3.48 4.37 V 5.366341
X Cyg DCEP 5.85 6.91 V 16.386332
SU Cyg DCEP 6.44 7.22 V 3.8455473
SZ Cyg DCEP 8.92 9.84 V 15.10965
Zet Gem DCEP 3.62 4.18 V 10.15073
BL Her CWB 9.70 10.62 V 1.307445
RX Lib CWA 11.65 12.78 V 24.933
T Mon DCEP 5.58 6.62 V 27.024649
SV Mon DCEP 7.61 8.88 V 15.23278
Y Oph DCEPS 5.87 6.46 V 17.12413
SV Per DCEP 8.49 9.37 V 11.129318
X Pup DCEP 7.82 9.24 V 25.961
RS Pup DCEP 6.52 7.67 V 41.3876
ST Pup CWA 9.28 10.68 V 18.73
Z Sct DCEP 9.05 10.16 V 12.901325
RU Sct DCEP 8.82 10.02 V 19.70062
W Vir CWA 9.46 10.75 V 17.2736
XX Vir CWB or AHB1 11.55 12.78 V 1.3482051
AL Vir CWA 9.1 9.92 V 10.30256
S Vul DCEP 8.69 9.42 V 68.464
SV Vul DCEP 6.72 7.79 V 45.0121


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

Star Name Type Magnitude Range Period (days) Comment / Reference
Polaris (alpha UMi) DCEPS 1.97 - 2.00 3.97 Amplitude has shrunk to almost zero in the last several decades but appears to be increasing now
beta Dor DCEP 3.46 – 4.08 9.843  
RT Aur DCEP 5.00 – 5.82 3.728  
ASAS182612   11.51 – 11.98 4.151 Eclipsing Cepheid; AAVSO Alert Notice #351
FF Aql DCEPS 5.18 – 5.68 4.471  
U Aql DCEP 6.08 – 6.86 7.024  
TW Cap CWA 9.95 – 11.28 28.61 JAAVSO, 10: 66 (DeYoung 1981)