The Blue Filtered Crab Nebula
When you look at the Crab Nebula through the blue window on your filter
wheel it is easy to see that most of the blue light passes
through the blue cellophane. The red and other colored light is mostly
absorbed. This is why the cellophane looks blue to us. It is absorbing all
colors except blue. What do you expect the Crab nebula to look like
through the red cellphane?
When you have viewed all the filtered images let's discuss why filters are useful.
Yellow Filtered Crab
Red Filtered Crab