Variable stars,photoelectric photometry,science education,and the A.A.V.S.O.

The role of amateurs and small-scale equipment in astronomical photometry is reviewed. The value of suitably selected projects for both research and educational purposes is stressed. Recent technical developments are noted, and a brief extrapolation to possible future arrangements included.Keynote address at the conference     

Comment on: Constraints on the depth and variability of the lunar regolith,by B. B. Wilcox,M. S. Robinson,P. C. Thomas,and B. R. Hawke

Abstract— Any permanent presence on the Moon will require use of materials from the lunar regolith, the surface soil layer on the Moon. Thus, knowledge of the thickness of the lunar regolith is essential. It has been proposed that crater counts obtained from high Sun angle photography give larger estimates of impact crater equilibrium diameters than for low Sun angle photography, and thus deeper estimates of lunar surface regolith than were previously made using crater morphology, size of blocky rimmed craters, and equilibrium diameters determined on low Sun angle images. The purpose of this comment is to evaluate this result as a means of resolving this important question before planning for future lunar missions is undertaken     

Vince Mannings,A. P. Boss,and S. S. Russell: Protostars and Planet,IV, Space Science Series

Earth, Moon, and Planets -     

Lunar occultation of Saturn. I. The diameters of Tethys,Dione, Rhea,Titan, and Iapetus

The diameters of Tethys, Dione, Rhea, Titan and Iapetus were determined from observations of their March 30, 1974, lunar occultations, made with the Mauna Kea 224 and 61 cm telescopes. Light curves were obtained simultaneously in four colors, and the difference between the time of occultation at the two telescopes provided a direct measurement of the slope of the lunar limb, found to be small in all cases. The satellite diameters were determined by least-squares fits of model occultation light curves to the data. In these fits the diameter and degree of limb darkening of the satellite are correlated variables, requiring the limb darkening to be specified before the diameter can be determined, or vice versa. However, for Titan the signal-to-noise ratio is sufficiently high to allow some assessment of the amount of limb darkening, which was found to be substantial. Titan's diameter must be at least 5800 km, much larger than the currently accepted value of 5000 km, making it the largest satellite in the solar system. This larger diameter implies a low mean density. For the other four satellites arguments are presented in favor of accepting the occultation diameters corresponding to limb darkened disks. Except for Titan, the lunar occultation diameters generally agree with previous diskmeter and radiometric determinations.