给它安装无线电设备是很困难的，而且仅凭肉眼观测也太不可靠，无法对它的行为进行确切的观察。
Attaching radio devices to it is difficult, and visual sightings are too unreliable to give real insight into its behavior.
单凭肉眼是观测不到海王星的。
因为有些是凭肉眼很难判断的。
Because some are very difficult to judge with the naked eye.
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