The main goal of this work is to have a better understanding of the problems and characteristics of photometric surveys with small-sized affordable equipment, like the one available at the Astrophysics Division/INPE, in São José dos Campos, Brazil. The use of low-cost instruments is appealing in the context of the detection of Extrasolar Planets (ESP), in the sense that many observers are available for survey and follow-up programmes. It could also make possible the inclusion of many developing countries in the search for planetary transits. We describe the data collection and analysis procedure for differential photometry of the transit of HD 209458 b, using a small telescope and a commercial CCD camera. According to the HST observations of Brown et al. (2001), the transit produces a box-shaped light curve with 2% depth and 184-min duration. The orbital period is ∼ 3.5 days. The equipment consists of a f/10, 11” Schmidt-Cassegrain Celestron telescope equipped with a SBIG ST7E CCD camera. Since the seeing at the campus is quite poor, we used a focal reducer to produce an effective focal ratio of about f/5, still keeping a good sampling of the PSF but with a larger field of view. The larger field of view allows the simultaneous observation of a relatively bright nearby star, suitable for differential photometry. We discuss the IRAF reduction procedures for the large number of images collected and present the results obtained in the transit of September 8, 2004