The dark dome of the Planetarium has been illuminated by numerous research studies across the decades, many of which follow similar questions in different settings. The question ‘Where does the planetarium optimally lie on the spectrum between education and entertainment?’ is frequently posed by researchers in the field, but seems rarely to be the central focus of the investigation. In order to approach an answer this question, I contacted a number of ‘Planetarium Professionals’ who perform diverse roles in diverse institutions. I conducted in-depth interviews exploring how they themselves conceived of their work and the implicit tensions it includes. From their insights I have developed a model showing some of the ways in which Planetarium Professionals think about their work in order to be successful.