Why does the moon turn red during a lunar eclipse?

I was just wondering why the moon turns red during a lunar eclipse

the atmosphere filters blue light and the indirect light the reaches the moon gives off and orange or reddish tint... depending on how much dust and clouds in the atomosphere

According to NASA, it's because of the earth's shadow - what you're seeing is every sunrise and sunset on Earth--all at once.

It has nothing to do with dust or filtering.