Polar mesospheric, or noctilucent ("night shining"), clouds usually are seen at twilight, following the setting of the sun below the horizon and darkening of Earth's surface.
极地气层云，或者说晚霞，通常是那些在黎明前看到的云朵，伴随着地平线以下落幕的太阳和黑暗的地球表面。
2
It is known as the Ombra Della Sera, or shadow of the Night, presumably because it looks like the long shadow cast by a person at twilight.
它以ombra della Sera或者夜晚的影子而著名，大概是因为它看起来像是暮光中人被拉长的身影。
3
In the twilight, in the evening, in the black and dark night.