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
별의 시경을 측정하는 것은 천문학에서 중요하다.byeol-ui sigyeong-eul cheugjeonghaneun geos-eun cheonmunhak-eseo jung-yohada.Measuring the right ascension of stars is important in astronomy.