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