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In mid-1990, a group of staff members of CTIO and the University of Chile initiated a photographic search on the CTIO Curtis/Schmidt telescope that was designed to discover supernovae (SNe) near maximum light, with the aim to study the physical evolution of the supernova explosion, the environmental factors affecting the occurrence of supernovae, and the general usefulness of this class of objects as distance indicators. By monitoring a large number of fields (45 fields of 25 sq-deg each), the Cal\'an/Tololo survey has yielded about 3 SNe per month to the limit of $B_{MAX} \leq 19.5$ which corresponds to a redshift range of (0.01$\la$z$\la$0.1). To date, we have found 29 Ia SNe, 2 Type Ic, 15 Type II, and one peculiar SN. From spectroscopy and photometry of these SNe, we have verified that most events were caught before maximum or within a week of maximum light. Once discovered, all SNe were regularly observed on the CTIO 0.9m telescope in the $BVRI$ system to produce light curves down to $B\sim22$.
The accurate magnitudes of these SNe, measured using psf fitting with DAOPHOT after the careful subtraction of the background galaxy, allow us to explore the range of variations in supernova light curve evolution. As examples, we present the light curves of the SNe 1990af (z=0.05) and 1992aq (z=0.101) which are two of the most distant SNe Ia ever observed through maximum light. A further example is the pair of Type Ia SNe (92bc and 92bo) at $z=0.020$ which have remarkably different light curve shapes: shapes which are apparently correlated to the intrinsic supernova luminosity at maximum light.
This research has been supported by Grant 92/0312 from Fondo Nacional de Ciencias y Tecnolog\'{\i}a (FONDECYT-Chile).
