This paper reports on an experience undertook by a small research team at Padova University at an astronomy conference at the Genova annual Festival of Science 2011. Our intent was to use Twitter to promote the event through totally new categories of possible interested audiences, to engage them, and to fine-tune the communication. To get acquainted with the hypothetical audience’s favorite issues we investigated Twitter‘s backchannel and focused our search on the keywords related both to the lecture topic and to the most popular hashtags used by influential tweeters. We threaded and tagged conversations, shared URLs to a dedicated website we designed for in-depth discussion of some selected topics, and polled people to find out their knowledge of the session topic and to generate stronger engagement. The results were encouraging, we reached a huge amount of interested people we would not have found with traditional audience segmentation methods and we have been able to find out their interests to fine-tune the lecture main topic.