Black Friday: lifetime access is on a special offer in the app, until November 30. Black Friday: special offer on lifetime access, until November 30. Download
광관의 장치는 태양의 코로나를 관찰하는 데 사용됩니다.gwanggwan-ui jangchi-neun taeyang-ui corona-reul gwansalhaneun de sayongdoemnida.The coronagraph device is used to observe the sun's corona.