欧洲全天候流星网络
The European AllSky7 fireball network

原始链接: https://www.allsky7.net/#archive

该流星观测网络使用由迈克·汉基设计的AllSky7系统,详细信息见2020年流星体会议论文。每个系统配备七个高灵敏度NetSurveillance NVT摄像头——五个用于广阔天空的覆盖,两个集中在南北方向,实现从地平线到天空的全面监控。 这些摄像头以25帧/秒的速度记录,极限星等为4,在典型的欧洲条件下,每年可捕捉约5000颗流星。数据由运行Ubuntu和专用AllSky7软件的迷你电脑处理,该软件自动分析夜间录像。 该软件可供网络成员免费使用,处理从误检去除和天体测量到使用多个站点的数据进行轨迹和轨道计算的所有内容。该系统的设计,包括内部穹顶涂装和以太网供电,可最大限度地减少反射并简化连接。

一场在Hacker News上的讨论围绕着欧洲AllSky7流星网络(allsky7.net),这是一个捕捉流星的摄像头系统。用户对该网络能够以足够精确度预测陨石着陆点,从而进行回收作业的能力印象深刻,并质疑在陨石进入大气层之前如何实现这种精确度。 对话延伸到迷人且有时被错误识别的流星观测现象——一些人戏称它们与不明飞行物报告有关。一个技术问题是关于该网络对自动生成图像的版权声明,用户们争论着类似监控录像的素材是否可以合法地享有版权。 最后,一位用户分享了一种替代的开源软件“indi-allsky”,用于捕捉类似的夜空图像,强调了即使在像树莓派这样的平台上,这些项目的可访问性。
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原文

The network is based on the AllSky7 systems manufactured by Mike Hankey. Details about the systems were published in a paper at Meteoroids 2020 conference.

Each system contains seven highly sensitive NetSurveillance NVT cameras with the SONY STARVIS IMX291 CMOS Sensor and a 4 mm f/1.0 lens. Five of them are horizonally oriented at an altitude of about 25°, camera six and seven point in northern and southern direction at an altitude of about 70° All together they cover the full sky down to the horizon.

Each camera has a field of view of about 45x80°. The cameras are recording at 25 fps and reach a limiting magnitude of about 4 mag. Maximum resolution is 25 pixel/°.

Beside the cameras, the dome contains a power supply and an ethernet switch for each camera. Each camera has a black paper baffle. The dome is painted from the inside with two color layers - silver outside and pale black inside. That reduces internal reflections and the thermal influx.

Power is supplied via Power-over-Ethernet (PoE), so that the whole system needs just one CAT-6 Ethernet cable to connect it to base computer. The computer is a barebone Mini PC running Ubuntu and the AllSky7 software by Mike Hankey, which is continuously improved. Each camera provides an SD (704x576 pixel) and HD (1920x1080 pixel) video stream which are recorded by the Mini PC and analysed asynchronously.

The camera is recording meteors and fireballs 24/7, but at the moment only the nighttime recordings are automatically analysed. About 5.000 meteors are recorded per year under typical central European conditions.

The software provided by Mike Hankey covers all aspects of the measurement of fireballs. It allows to sort out false detections from the daily meteor stack, to measure the position of fireballs in single video frames, to identify reference stars and do the astrometry and photometry of the recording, and to combine the observation with data from other camera stations to calculate trajectories and orbits. The software comes free of charge for all members of the AllSky7 Firebal Network (community license). All software functions are shown in a short advertising film.

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