Caption: Winner in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   As Earth moves around the Sun, the positions of the stars in the night sky appear to change over the course of the year. This is well exemplified in this mosaic, with images taken in all four seasons throughout 2020 in the region of Veneto, Italy, showing the apparent motion of the Ursa Minor and Ursa Major constellations. Ursa Minor, the Little Bear, is a constellation of the northern hemisphere, and it contains the northern celestial pole, in our current epoch marked by a bright star called Polaris or the Pole Star. For centuries Polaris has been used for navigation in the northern hemisphere, as it has been almost at the exact pole position for roughly 200 years. In the Middle Ages and antiquity, there was no pole star; the celestial north pole lay in a dark region and the Greeks considered the “Little She-Bear” as a companion of the “Great She-Bear”, which is more easily recognizable. The brightest stars of these constellations were alternatively also considered as chariots by the Greeks, as written in Aratus’s famous didactic poem from the 3rd century before the common era. The most famous asterism in Ursa Major, composed of seven stars, has different names across the (northern) world. While considered as a chariot by the Greeks, it is “The Northern Dipper” in China, and “The Seven Oxen” for the ancient Romans. It was also the navigational purpose that led to the name The Great She-Bear, Ursa Major; for the Greeks, travelling towards the direction of the horizon above which Ursa Major appears meant moving towards the land of the bears (northern Europe). An animal is clearly recognizable when taking into account all the fainter stars in the vicinity of the seven bright ones. They considered it a female bear because Greek mythology connects this animal with the nymph Callisto, whose story describes the initiation rituals for women. In the top left, we see an image taken on a spring evening, while the image below shows the same portion of the sky on a summer evening. Going counterclockwise, we see the sky during autumn in the bottom right image, while the top right finally shows this portion of the sky in the winter. Note that the relative positions of Ursa Minor and the Big Dipper don’t change, but all stars appear to be moved in a circle around Polaris. This star pointing due north lies at the point where Earth’s rotational axis intersects the celestial sphere. The shift of constellations throughout the year is therefore a globe-clock or a globe-calendar, used by ancient civilizations to measure the year, and to predict the changes of seasons. It helps to establish, for instance, the best time for sowing and sailing as winds change with the seasons.
Credit: Giorgia Hofer/IAU OAE

Caption: 這張令人歎為觀止的照片是 2020 年 6 月 25 日在印度尼西亞西爪哇庫寧安省西里穆斯市凌加梅卡村的晴朗夜空下拍攝的，照片中的星軌掠過南半球的天際。星軌是地球自轉所導致的恆星表觀運動，當長時間跟蹤時，就會產生這些令人著迷的光弧。因為這張照片是在赤道附近拍攝的，所以恆星所圍繞旋轉的點（南天極）靠近地平線。攝影師使用智能手機上的星軌功能，在較長時間內拍攝了一系列圖像，並將它們疊加在一起。前景引人注目的大樹增添了畫面的深度，使上方天體的運動與地面的靜止形成了鮮明對比，同時也遮掩了周圍的一些光汙染。世界不同地區的夜空景色各異，令人驚嘆，使人們意識到保護各地黑暗天空的重要性。
Credit: Slamat Riyadi/IAU OAE (CC BY 4.0)

Caption: This video shows the Milky Way’s sprawling brilliance across the celestial expanse. Among the stars’ grand theatre, the Southern Cross constellation claims its place in the scene, distinguished by its distinctive cross shape as seen in the top of this video and slightly to the right just over the Milky Way, slowly disappearing as the video progresses. This celestial marker, a prominent feature in the southern hemisphere, holds cultural and navigational significance, having served as a navigational guidepost for centuries. Accompanying the Milky Way’s grandeur are the two Magellanic clouds, celestial companions seen dancing in the distant sky. The Carina Nebula adds its ethereal glow to the cosmic panorama, painting a radiant hue against the darkness. In the midst of this celestial ballet, a gentle green hue envelops the atmosphere, a phenomenon known as airglow, adding a touch of subtle luminescence to the night sky. The terrestrial also makes an appearance, with planes flying overhead and vehicles driving between observatory buildings. This time-lapse, taken from the La Silla Observatory in Chile, is a window to the captivating dance of stars, offering a glimpse into the awe-inspiring beauty of our galaxy and the celestial landmarks that grace the southern sky.
Credit: José Rodrigues/IAU OAE (CC BY 4.0)

Caption: Taken from San Pedro de Atacama, Chile, in June 2023, this time-lapse reveals the celestial ballet that unfolds as the Southern Cross takes its majestic journey across the sky, pointing the way to the South Celestial Pole around which the sky rotates, until it gracefully sets. The star-studded canvas showcases the grandeur of the Milky Way, adorned by the rotating Large and Small Magellanic Clouds swirling around the Southern Celestial Pole. The prominent constellations of Crux, Centaurus, Scorpius, and the former Argo Navis (Carina, Puppis, Vela) are also visible. The spectacle begins just after nightfall, capturing the radiant descent of Canopus, a beacon about to dip below the horizon. Throughout the sequence, there is a subtle presence of passing aeroplanes, fleeting headlights of cars, drifting clouds, and the ethereal airglow. At a stunning moment, a vivid meteor streaked across the sky, a breathtaking fireball briefly igniting the right lower corner around the 41st second mark. As the sequence progresses, the rising moon elegantly illuminates the landscape, casting its glow upon an ancient tree trunk resting on the dry, dusty grounds of the Salar de Atacama. This captivating journey through the night skies concludes before the break of dawn, offering a glimpse into the celestial marvels that are woven into the nocturnal tapestry of San Pedro de Atacama.
Credit: Uwe Reichert/IAU OAE (CC BY 4.0)

Caption: This time-lapse captures the movement of the stars alongside the majestic 64-metre Sardinia Radio Telescope (SRT) from the National Institute of Astrophysics (INAF), with special attention to the renowned Big Dipper against the backdrop of the celestial sphere. The camera pans as the famous asterism sinks in the sky while planes fly past and the radio telescope rotates. The harmonious interplay between the stellar pathways and the colossal dish of the radio telescope creates a mesmerising visual ode to the cosmic ballet taken in September 2019.
Credit: Antonio Finazzi/IAU OAE (CC BY 4.0)

Caption: 這張拍攝於2022年10月的照片是在印度阿馬爾提亞村（Amartiya）帕諾提耶（Panotiya）的黑夜中拍攝的，展現了夜空中美麗的星軌。攝影師僅用一部智能手機和一個三腳架就捕捉到了這些星軌——它們是我們星球自轉的視覺證據，因為每一條星軌都代表著地球自轉時恆星的明顯運動，創造出令人著迷的宇宙光影編舞。恆星有不同的顏色，有的閃著藍光，有的泛白，暗示著它們不同的溫度和組成。此外，一架飛機的細微軌跡與永恆的星空之舞短暫的交匯在一起，寧靜的星空與下方熙熙攘攘的生命活動形成了鮮明對比。
Credit: Govind Gurjar/IAU OAE (CC BY 4.0)

Caption: The Big Dipper asterism gracefully moves above the otherworldly tufa formations of Mono Lake, California. The time-lapse captures the Big Dipper’s movement across the northern horizon until its inferior conjunction. At Mono Lake’s latitude (+38°), the stars of the Big Dipper remain circumpolar, except for Alkaid. The North Star sits 38° above the horizon, just outside the field of view in the top right. The lunar illumination bathes the landscape in a soft glow, gradually fading as the Moon sets, cloaking the scene in darkness.
Credit: Fabrizio Melandri/IAU OAE (CC BY 4.0)

Caption: A cosmic journey unfolds across continents in this time-lapse video which captures both iconic constellations from diverse corners of the world. Starting in China, the Big Dipper graces the night sky, a steadfast guide embedded in cultural narratives. Its luminance marks the beginning of this celestial odyssey. The two pointer stars on the end of the Big Dipper point to the North Star (Polaris) which appears to remain stationary as the sky rotates. From Nepal’s lofty peaks, the Big Dipper’s familiarity persists, a reliable fixture in the shifting panorama of the rotating planet. Moving to Chile, the Southern Cross adorns the firmament, emblematic of the southern skies. Frames from Chile showcase this constellation accompanied by the Milky Way Galaxy. In Namibia, a telescope from the H.E.S.S. Observatory appears in the video. Later, nestled beneath sheltering trees, the Big Dipper persists in its celestial prominence, appearing against a canvas of stars. Using varied techniques — fisheye lenses, static cameras, and Earth's movement-tracking — each frame unveils the Cross’s grandeur against diverse landscapes. These sequences — marked by star trails and Earth’s rotation—highlight the enduring presence of the Big Dipper and Southern Cross, bridging cultures and celestial beauty across hemispheres.
Credit: Jianfeng Dai/IAU OAE (CC BY 4.0)