Photoelectric observations of asteroids 3, 24, 60, 261, and 863

Abstract Observations of five asteroids, obtained from various observatories from 1978 to 1984, are presented. A Fourier analysis method was used to derive the composite lightcurves. This solution method yields a value for the rotation period, mean absolute magnitudes on each night of observation, and Fourier coefficients defining the shape of the composite lightcurve, to any degree specified. A major advantage of the method is that it yields formal error estimates for all the quantities computed. The Fourier coefficients derived can be used for studies of the shapes and pole orientations of asteroids and to define “rotation phase” in a more formal way, for connecting observations from one apparition to another. Periods, amplitudes, and phase relations are reported for four of the five asteroids. The presence of a substantial amplitude first harmonic in the lightcurves of 3 Juno, 24 Themis, and 60 Echo suggests that these asteroids may have significant surface albedo variegation. 60 Echo exhibits a difference of 0.2 magnitude in its mean absolute magnitude from different aspects, which suggests a somewhat polar-flattened figure. High-quality magnitude vs solar phase angle data were obtained for 24 Themis from 0°.3 to 21°. These data are perhaps the best available of a dark asteroid and provide a test for light-scattering theories.