Why do ground based planet transit searches give only a few detections so far?

Kurzfassung

After the first detection of the transiting extrasolar planet HD 209458b in 1999 more than 20 groundbased transit searches has been established. The expectations were high to find several hundreds of transiting hot Jupiters only in a few years. With the exception of OGLE candidates no secured detections have been reported so dar. Were these assumptions too optimistic or is there really a lack of transiting hot Jupiters? Based on our experience with the Berlin Exoplanet Search Telescope (BEST) the transit detection rates for groundbased searches are discussed. Aspects like the number of expected solar-like stars in the observed fields, geometrical probability, crowding, duty cycle, detection limits and optimized choice of the target fields are adressed with the aim to optimize observation strategies and instruments to reach higher transit detection rates.