66P/Du Toit

This comet was discovered Du Toit at Boydon Observatory (South Africa) on May 16th 1944. This was a very favourable apparition and the comet reached magnitude 10 and maintained that level of brightness for some three months. The comet was recognised as being of short period, but despite careful searches, the 1959 apparition was missed. The comet was recovered, although not without difficulty because of its faintness, in 1974, when Torres found it on plates at Cerro El Roble having initially not detected the images. The following apparition in 1988 was again missed, but the 2003 apparition, with perihelion on August 27th 2003 has again been more favourable.

66P/Du Toit has a period of 14.7 years with perihelion at 1.27AU. This means that a return at perihelic opposition can lead to a very favourable apparition. However, even when favourable, the diffuseness and lack of condensation of the coma makes observation more difficult than one would expect from its brightness.

The orbit is very stable at present. Only close encounters to Earth are possible and from 1800 to 2200 the closest encounter is at 0.45AU, with only minimal changes to the orbit as a consequence.

The light curve

The 2003 return was not particularly favourable as the minimum geocentric distance was 1.07AU. The light curve shows rapid brightening typical of a quite evolved comet, although with an important scatter. 66P/Du Toit was expected to brighten at almost a magnitude per month through the first half of 2003, with maximum brightness at perihelion.

Seichii Yoshida’s light curve suggests that there was a 2 magnitude outburst in July 2003, about a month and a half before perihelion. This though is not apparent in our data (left), because it stops before the date of outburst, when the comet was too close to the Sun for CCD observations.

The dust production data (Afrho) shows a rather flat distribution of values between T-120 days and T-80 days. A single point at an early date, but by a reliable observer, is somewhat fainter and leads to a r–3.0 fit for dust production with heliocentric distance, somewhat smaller than the normal approximately r–5 law, although over a very small range of heliocentric distance.












CCD observation in a 10 arcsecond aperture by:

·         Ramón Naves & Montse Campàs - MPC 213

·         Rolando Ligustri – MPC 235

·         Albert Sánchez – MPC 442

·         Quim Moreno – MPC A03