A large group of
observers studied the behavior of comet 9P/Tempel 1
before and after the DEEP IMPACT encounter, at Merate Observatory
and at SAS Observatory.
Close to the impact, the two Observatories obtained
high quality images at the same time in order to verify some
peculiar morphological structures.
Lorenzo Comolli, Cesare Guaita,
Giuseppe Macalli, Antonio Paganoni
Center, Tradate, Italy), Roberto
(FOAM13 Observatory, Tradate, Italy), Mauro Ghigo
(OAB, Observatory of
Brera-Merate, Merate, Italia), and Cristiano B. Cosmovici
for Space Physics-INAF, Rome, Italy) were observing at Merate.
Federico Manzini and Roberto Crippa
at SAS Observatory (Stazione Astronomica of Sozzago, Novara,
Italy), taking also a number of very precise astrometric
measurements in the weeks before the impact.
The Merate Groups used the 1,37m
Ruths Cassegrain reflector
, reducing the 15m focal lenght to
7.5m and applying at the focus a HiSIS43 CCD camera (Kodak Kaf 1600e
sensor), lent by Tradate FOAM13 Observatory (obtaining a resolution of
0,49”/pixel in binning 2x2). No filter was used.
The SAS Group used a HiSIS43 CCD camera (Kaf 1603ME sensor) applied to
a reflector of 0,4 m (f/6,8), (resolution of 0,71"/pixel).
At Merate, pre-impact images were taken on July 2nd and July 3rd,
post-impact images were taken on July 5th and July 6th (unfortunately
on July 4th Merate was under a strong thunderstorm). A minimum of 30
and a maximum of 150 images (single exposure time: 20s) were
In these images the magnitude of the false nucleus
decreased from 14,6 to 14 between July 2-3 and reached
m=13,7 an July 5.
At the same time, the shape and the dimension of the coma
appeared affected by natural events (outburst) before July 4th
and by the artificial event of the impact in the days immediately
after July 4th. In particular (Fig.1):
- a small deformation of the coma (maximum dimension of about 80”)
was observed on July 2nd, about 10h after a minor outburst.
- a strong variation of the dimension of the coma was
clearly visible 39h after the impact, increasing from 60” to
120” between July 3rd and July 5th but again decreasing to 25”
after 24h: this could be caused by the release and diffusion of the
artificially induced dust cloud.
Some interesting jet-like features found in
images from SAS on July 5th (Fig.2) were confirmed in the Merate images.
L.Comolli, C.Guaita, G.Macalli,
A.Paganoni (GAT Astronomical Center, Tradate, Italy)
R.Crippa (FOAM13, Tradate, Italy)
M.Ghigo (AOB, Merate, Italy)
C.B. Cosmovici ( INAF-IFSI, Roma,
F.Manzini (SAS Observatory,
|Fig. 1: Comet
Tempel as seen at Merate Obervatory (click
on the image for hi-res)
Comet Tempel as seen at SAS Observatory (click on the image for hi-res)
|Fig. 3: The
1.37m Ruths cassegrain telescope (click
on the image for hi-res)
|Fig. 4: A part
of the group of observers, from left: Lorenzo Comolli, Giuseppe
Macalli, Roberto Crippa, Lucia Guaita, Mauro Ghigo, Cesare Guaita. (click on the image for hi-res)
|Fig. 5: The CCD
camera at the focus of the 1.37m Ruths telescope, connected to the
acquisition PC. (click on the image