G.A.T. Press Release of  July 18, 2005

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  (GAT Astronomical Center, Tradate, Italy), Roberto Crippa (FOAM13 Observatory, Tradate, Italy), Mauro Ghigo (OAB, Observatory of Brera-Merate, Merate, Italia), and  Cristiano B. Cosmovici (Institute for Space Physics-INAF, Rome, Italy) were observing at Merate.
Federico Manzini and Roberto Crippa observed 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 stacked together.
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.

Observers:
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, Italy)
F.Manzini (SAS Observatory,  Novara, Italy)

Fig. 1: Comet Tempel as seen at Merate Obervatory (click on the image for hi-res)

Fig. 2: 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 for hi-res)