Presentiamo qui uno dei report inviati periodicamente dal GAT al
Central Bureau for Astronomical Telegrams,
INTERNATIONAL ASTRONOMICAL UNION. Per questo motivo il testo è in Inglese.
C/Hale-Bopp (1995 O1) observations.
from May 21 to September 15, 1996 : 0,335m reflector (f/4.8)
November 23.8 and 24.8, 1996 : 0.15 m reflector ( f/5)
CCD camera with pixels of 9 microns, without filter (spectral sensitivity:
0.8-1.1 microns).
Observations performed during 6 months, from May 21 to November 24 1996,
confirmed a regular increase of the C/Hale-Bopp cometary activity.
As a principal indication of this activity, we observed an increase
of the number and of the intensity of some spectacular jets coming from
the nuclear region . In particular we observed : 3 jets from May 21 to June
6, 4 jets from July 25 to August 4, 5 jets on August 4 and 8, 6 jets on
August 16, 7 jets from September 11 and 15, 8 jets on November 24.
After elaboration of our CCD pictures with the Larson-Sekanina algoritm and
a ring masking process, we derived these position angles (p.a.) : p.a.=65ø
for the principal jet (antisolar direction), p.a.=25ø and 95ø for the other
two more important jets (in lengh and brightness), p.a.= 110ø-165ø-220ø-280
-350 for other fainter and shorter jets.
The jet at p.a.=165ø appears to be broad and spread apart and it could be
produced by the perspective overlapping of two more collimated jets. This
interpretation is linked to the observation that all other jets seem very
narrow and collimated up to 1.5' from the nuclear region.
The complete analysis of all our observations demostrates that jets DON'T
SHOW ANY INTRINSIC ROTATION, the only rotation being linked to the change
of the Earth-Comet-Sun position angle.
Nickname of 'porcuspine comet' is, again, the best representation of this
extraordinary comet.
December 1, 1996
F.Manzini, R.Crippa and C.Guaita
STAZIONE ASTRONOMICA OF SOZZAGO
Member of a Consortium created by Prof. C.Cosmovici to coordinate
Italian studies about recent big comets.
