Our project of strategic partnership of planetariums „Scientists warn: Sufficient but not redundant lights!“ connects partners from 7 European neighboring countries. Planetariums - school, theater and film at once - are unique audiovisual facilities for the promotion and publicity of science. They are dedicated to education in technical and natural sciences, they encourage interest in these disciplines and critical thinking in public. With a few exceptions, sky, stars and space fascinate everybody: amateurs and professionals, the smallest and the oldest; looking at images from orbital stations or from the Moon has an obvious emotional charge. Space research and star observing are connected with a number of fundamental questions of human existence; it often extends into the philosophy and touches upon religious issues. Our project builds on previous cooperation and projects Erasmus+, and focuses on astronomy and on the sustainable development of a high-quality environment, friendly to both humans and fauna and flora. We would like to make the public sensitive and draw attention to the seriousness of light pollution. The project fits into the ideas of the Space Strategy for Europe.Each of the partners is a leader for lifelong learning in its region and the joint project will enable them to follow international cooperation with a large outreach. In accordance with the horizontal priority of the Erasmus Open programme and innovative practices in a digital era as well as environmental and climate goals, the subject of our project is extending and developing the competences of educators and other personell who support adult learners in planetariums - our operators, teachers, technicians, authors, media specialists, scientists. Partial focuses of cooperation will include getting to know the conditions and the process of creating innovative fulldome programmes in major planetariums, the appearance and daily operation of interactive exhibitions, the digital projection technology including its technical aspects, further development, etc.; also getting to know the system of individual education in astronomy, and especially cooperation on creating the joint intellectual output - the program for digitaria in the so-called full dome format, which will be transferable and compatible.The project is innovative in many ways: connecting the makers to produce a transferable program for digitariums is an extremely challenging step in the field of ICT; but it is also efficient in terms of costs and resources. The resulting program in seven language versions, shared by dozens of planetariums, will bring about considerable cost savings, while embracing hundreds of thousands of spectators. Innovative is also the use of synergies for a pan-European awareness campaign to save the dark sky. International cooperation will deepen among the partners, who are experts in this method of audiovisual projection in their respective states. European Planetariums are mostly financed by public funds. This project will enable them to share a superior program for a wide range of visitors - and share costs. Newly acquired information, knowledge and experience from visits to partner institutions (shadowing, professional discussion) and from the joint production of the digital program will be used by the involved partners also in the creation of other new educational programs for all age groups of their regular as well as random visitors. By this, they will contribute to the development of lifelong learning not only in the cities, where the involved planetariums are located, but also in entire regions, where these institutions have their exclusivity.The total of 8 project meetings will take place to enable the transfer of know-how and good practice and during the preparation of the product according to the defined technical parameters; each time 2 educators from each partner country and 3 local experts (together 96) will participate in the meetings. We also plan one multiplier event with the participation of 75 people at least. 15 employees will be involved in the product creation according to the above methodology; i.e. there will be a total of 186 supported experts, who will participate in a unique mindset output and its international dissemination.The resulting synergies can be used in the creation of another joint output; after the project termination, we expect further networking and cooperation at the international level and we intend to continue working together to protect the dark sky, not just for astronomers here and now, but for all mankind in the future.