Caption: 国际天文学联合会 OAE 天文摄影比赛星轨类第三名。 这张壮观的图片捕捉到了大自然最富戏剧性的表现形式--火山爆发和夜空。前景中的火山是埃特纳火山，位于意大利西西里岛，于 2021 年 2 月喷发。在背景中，我们可以看到地球绕假想轴转动产生的星轨。由于埃特纳火山位于北纬 37°左右，我们会注意到空中的弧线相当平缓，因为这里远离北极，从那里看天空轨迹会呈现接近圆形的形状。当我们从南半球或北半球向赤道移动时，星轨逐渐由圆形变为更加平行的线条，这是因为观察者逐渐远离指向地球自转轴之一的天顶位置。因此，天空为我们提供了有关位置和时间的宝贵信息，也是古代文明追踪天体运动的重要实践。这幅图像还捕捉到了恒星因温度不同而产生的不同颜色：温度较低的星为白色和红色，而温度较高的恒星更蓝。
Credit: Dario Giannobile/IAU OAE

Caption: 国际天文学联合会 OAE 天文摄影比赛星轨类第二名。 天文学即使不是最古老的科学，也是其中之一，因此千百年来与各种文化都有着千丝万缕的联系。这张图片以巨石阵为背景，在某种程度上传达了这种联系。关于天文学家所说的考古天文学遗址，以及它们与天空的联系（如季节、月相等），有很多研究。古今中外的文明对天空中的景象都有自己的看法和解释，这不仅与文化有关，也与人们的日常活动和季节活动有关。通常被称为 "星轨 "的 "同心圆 "是天空视运动的结果，实际上是地球自转的结果。图像中心上方出现的小点是Polaris--北极星。只有北半球的观测者才能看到北极星。北极星的高度可以用来推断观测者的实际纬度。巨石阵位于北纬 51°左右。这张照片摄于世界上最著名的古代遗址之一，它把我们带回了过去，让我们对千年前生活在那里的人们所讲述的故事产生了好奇。
Credit: Till Credner/IAU OAE

Caption: First place in the IAU OAE Astrophotography Contest, category Star trails. This star trail image shows the apparent movement of the stars in the night sky, which results from the Earth’s rotation around its polar axis. The trees in the foreground serve as an anchor as we turn with the Earth. The bright white semi-circle in the center of the image is the North (Pole) star – Polaris, which is located very close to the North Celestial Pole. One way to imagine that the Earth is at center of hollow crystal sphere, and the stars are embedded on this sphere, as the Earth spins on its axis, an observer on Earth sees the stars rising and setting, following an arc, because the horizon prevents the observer from the full arc for stars that are further away from the Celestial Pole. The North Celestial Pole (and its opposite the South Celestial Pole) is essentially formed by extending the line of the Earth’s axis. Capturing this image requires the photographer to take a long exposure with the camera on a tripod and pointing towards the Pole Star (North Hemisphere). In the Southern Hemisphere there is no star as close as Polaris is to the Celestial Pole, so the position of the South Celestial Pole is found using the South Cross and Pointer Stars (Alpha and Beta Centauri). Although overall the image has a slight blue tint, it does capture the varying colours of stars, it is easy to distinguish between the higher temperature blue stars and the lower temperature of the whitish stars, and even lower temperature reddish stars. The reason for this variation in colour is because higher temperature stars emit more in shorter wavelengths (bluer), compared to lower temperature stars which emit in longer wavelengths (redder).
Credit: Fabrizio Melandri/IAU OAE