Citizen science is a way of doing science in which people who do not necessarily have previous training to be part of a scientific project are invited. One of the challenges presented by citizen science is the training of volunteers in the tasks required by the research project. A valid approach is through gamification strategies. Gamification is the use of game elements in contexts that were not intended to be a game. In this article, we present a study of the use of gamification in tutorials for a citizen science project of astronomy photo classification. The evaluations showed that the aesthetics, the evaluation by points, the promotion with badges and the competition have been promising elements in this type of tutorials.