Caption: Gagnant du concours d'astrophotographie 2023 de l'UAI OAE, catégorie Images fixes avec smartphones-appareils mobiles : Traînée d'étoiles dans l'hémisphère sud avec pollution lumineuse à un niveau 4 sur l'échelle de Bortle, par Slamat Riyadi. Cette photo, à couper le souffle, prise sous le ciel nocturne clair du village de Linggamekar, Cilimus, Kuningan, Java occidental, Indonésie, le 25 juin 2020, montre des traînées d'étoiles balayant les cieux de l'hémisphère sud. Elle est l'une des six lauréates dans la catégorie des images fixes prises exclusivement avec des smartphones/appareils mobiles. Les traînées d'étoiles sont dues à la rotation de la Terre qui provoque le mouvement apparent des étoiles, créant ces arcs de lumière envoûtants lorsqu'ils sont suivis sur de longues périodes. Ici, le point autour duquel tournent les étoiles (le pôle céleste sud) est proche de l'horizon, car l'image a été prise près de l'équateur. Le photographe a utilisé la fonction de suivi des étoiles d'un smartphone, qui a capturé une série d'images sur une période prolongée et les a empilées. L'arbre remarquable au premier plan ajoute de la profondeur à l'image, contrastant avec le mouvement céleste et l'immobilité terrestre, tout en masquant une partie de la pollution lumineuse environnante. Les différentes régions du monde offrent des perspectives variées et étonnantes sur le ciel nocturne, soulignant l'importance de préserver le ciel noir partout dans le monde.
Credit: Slamat Riyadi/UAI OAE (CC BY 4.0)

Caption: This time-lapse documents the trajectory of the iconic Big Dipper across three frames taken in July 2020. Captured from three locations in Italy, Tre Cime di Lavaredo Auronzo di Cadore, Monte Rite, Cibiana di Cadore, and Casera Razzo, Vigo di Cadore, this visual odyssey showcases the captivating journey of the Big Dipper with the addition of trails of stars painting a celestial canvas. It not only traces the path of this renowned asterism but also features the rare appearance of comet Neowise C/2020 F3, an extraordinary event that graced our skies during July 2020.
Credit: Giorgia Hofer/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: Taken in the darkness of Panotiya, Amartiya village, India, this image from October 2022 showcases beautiful star trails painting the night sky. With only a smartphone and a tripod, the photographer captured these trails — visual evidence of our planet's rotation, as each streak represents the apparent movement of the stars as the Earth spins, creating a captivating cosmic choreography of light. The distinct colours of the stars — some gleaming blue, others whitish — hint at their varying temperatures and compositions. Additionally, a subtle streak of an aeroplane momentarily intersects the timeless dance of the stars, juxtaposing the serene heavens with the bustling activity of life below.
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)

Caption: Beneath the celestial ballet of star trails that weave their way across the night sky, the Beijing Forbidden City stands as a testament to ancient celestial connections in this image captured in March 2022. Designed with a cosmic alignment in mind, the palace echoes the orientation of the North Star, also known as Polaris, a celestial anchor that has long guided navigators and symbolised steadiness in the sky. It was believed that the Emperor embodied the earthly representation of this pole star, bridging the realms between heaven and earth. In this harmonious one-hour exposure captured with a smartphone, the streaks of stars trace their nightly journey across the firmament, converging toward the North Star, reflecting the precision of both architectural design and celestial paths.
Credit: Stephanie Ziyi Ye/IAU OAE (CC BY 4.0)