The Coma: How to Estimate Its Brightness and Record Its Features

Abstract

Making brightness estimates of comets is the most useful project for the visual comet observer. Careful monitoring of the intrinsic brightness of short-period comets is essential in determining changes that may occur over time, and contemporary visual observation is the only safe way of comparing the brightness of a periodic comet as it appears today with the observations of yesteryear. Moreover, brightness estimates of long-period comets tell us how these objects evolve as they approach the Sun and recede again from it and enable comparison to be made between the photometric development of comets having different lengths of period. Again, a careful watch on comet brightness by visual observers may find that a certain comet’s brightness is fluctuating on a short time scale, and it might be possible to determine whether such short-period fluctuations are correlated with solar activity or even with the rotation of the comet’s nucleus.