Cincinnati Observatory

The differential correction of nearly parabolic orbits was discussed by the author (Herget, 1939) in the era of lead pencil computing. The Gauss-Marth method is the best one to use whenever the appropriate conditions exist, i.e., |E| < 64° and e nearly unity. The crucial point in the above-cited discussion is the use of the first differences from the Gauss-Marth tables in order to simplify the computation of the partial differential coefficients, namely dB/dA, dC/dA, and dD/dA.

The orbit of P/Pons-Brooks has been studied using the observations of 1812, 1883–1884 and 1953–1954. A curious deviation of the residuals has been established during the last two months of observation in April and May 1884, but no discontinuity in the orbit due to an impulsive action on the comet has been found. The observations covering two complete revolutions cannot be fitted into one single orbit.