The observations of comet C/1998 H1 (Stonehouse) indicate a very slow brightness decrease according to the formula
Because this comet had just reached its minimum distance from earth and sun at discovery the brightness decreased continually, starting at 10.5m.
Due to the small distance to earth (minimum 0.55 AU) the comet displayed a 6' coma at discovery. With the distance earth - comet increasing it decreased to 1' at the end of the apparition. The absolute coma diameter measured about 130.000 km, diminishing only in the last phase to 110.000 km. Consequently, the decreasing apparent coma diameter represented the increasing distance to earth. However, the coma itself was rather diffuse, the degree of condensation decreased from DC 3 to DC 1.
Total Brightness and Coma Diameter
Andreas Kammerer
