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Multi-wavelength CCD photometry over 21 years has been used to produce deepcolor-magnitude diagrams together with light curves for the variables in theGalactic globular cluster NGC 5824. Twenty-one new cluster RR Lyrae stars areidentified, bringing the total to 47, of which 42 have reliable periodsdetermined for the first time. The color-magnitude diagram is matched usingBaSTI isochrones with age of $13$~Gyr. and reddening is found to be $E(B-V) =0.15 \pm0.02$; using the period-Wesenheit relation in two colors the distancemodulus is $(m-M)_0=17.45 \pm 0.07$ corresponding to a distance of 30.9 Kpc.The observations show no signs of populations that are significantly youngerthan the $13$~Gyr stars. The width of the red giant branch does not allow for aspread in [Fe/H] greater than $\sigma = 0.05$ dex, and there is no photometricevidence for widened or parallel sequences. The $V, c_{UBI}$ pseudo-colormagnitude diagram shows a bifurcation of the red giant branch that by analogywith other clusters is interpreted as being due to differing spectralsignatures of the first (75\%) and second (25\%) generations of stars whose agedifference is close enough that main sequence turnoffs in the color-magnitudediagram are unresolved. The cluster main sequence is visible against thebackground out to a radial distance of $\sim17$ arcmin. We conclude that NGC5824 appears to be a classical Oosterhoff Type II globular cluster, withoutovert signs of being a remnant of a now-disrupted dwarf galaxy.

A Photometric Study of the Outer Halo Globular Cluster NGC 5824