Can you see the Earth’s penumbra through visual observations?

It is possible by decreasing the brightness of the eastern side of the Moon’s disk before the beginning of the particular phase and, accordingly, the western side after the end of the particular phase.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.