用肉眼观察的方法，隔周一次观察皮肤的外观状态和皱纹数；
Visible changes in the skin including wrinkling, sagging and erythema were observed every other week.
从一端到另一端，银河系布满星星的圆盘横跨12万光年，可以用肉眼和光学望远镜观察到。
From end to end, the Milky Way's starry disk, observable with the naked eye and through optical telescopes, spans 120,000 light-years.
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.
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