AbstractRR Lyraes are pulsating stars lying on the horizontal branch of the HR diagram. They are typically found in globular clusters and are some of the oldest objects in our Galaxy. Constraining their age and knowing their absolute magnitude is important for constraining the age of the Universe and for establishing a distance scale. A crucial role in this is their metallicity - the amount of elements other than hydrogen and helium that they contain. Traditionally the way to estimate the metallicity of a star was through spectroscopy. But RR Lyraes pulsate with a regularly repeating light curve. Astronomers have found relationships between the structure of their regularly repeating light curve and spectroscopic metallicities. Here we study data for RR Lyraes observed by the CTSTAR telescope at Antarctica. The advantage of such a telescope is the long polar night that allows for long uninterrupted time series of observations. Here we Fourier decompose RR Lyrae light curve data obtained from CTSTAR telescope and obtain metallicities using the structure of the light curve and compare with existing results in the literature.