Visible light telescopes can resolve a piece of sky just a few arc seconds across — at least 60 times a smaller patch of sky than can be resolved with the human eye.
光学望远镜在数角秒内就能获取一张星空图—至少比肉眼能获取的大60倍。
2
Tips: stick to the end of the cloth is level, don't post into arc, open your eyes to pull carry eye end.
Tips：贴布的尾端要呈水平，不要贴成弧形，睁眼时就能拉提眼尾。
3
Several arc echoes at the posterior segment of eye were detected in the silicon-oil-filling eyes with retinal detachment.