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With the aid of the All Sky Automated Survey (ASAS) database on the Galacticfield, we compare the iron abundances of fundamental mode RR Lyrae starsderived from the Fourier parameters with those obtained from low-dispersionspectroscopy. We show from a set of 79 stars, distinct from the originalcalibrating sample of the Fourier method and selected without quality control,that almost all discrepant estimates are the results of some defects orpeculiarities either in the photometry or in the spectroscopy. Omitting objectsdeviating by more than 0.4dex, the remaining subsample of 64 stars yieldsFourier abundances that fit the spectroscopic ones with a standard deviation of0.20dex. Other, more stringent selection criteria and different Fourierdecompositions lead to smaller subsamples and concomitant better agreement,down to 0.16dex standard deviation. Except perhaps for two variables among the163 stars, comprised of the ASAS variables and those of the originalcalibrating set of the Fourier method, all discrepant values can be accountedfor by observational noise and insufficient data coverage. We suggest that theagreement can be further improved when new, more accurate spectroscopic databecome available for a test with the best photometric data. As a by-product ofthis analysis, we also compute revised periods and select Blazhko variables.Comment: 12 pages, 8 figures, to appear in Astronomy and Astrophysic

Iron abundances derived from RR Lyrae light curves and low-dispersion spectroscopy