What is chromatic aberration?
This is a defect with ordinary lenses.White light contains 7 colors and ordinary lens can not focus all colors at same point.
Due to differences in Wave length the 7 colors focus at didfferent points.If you use this lens the stars will appear like rainbow color .
picture credit photographylife.com.
At an elementary level we often teach that the refraction of light is independent of frequency, but that is obviously false, otherwise prisms would not split white light into colours.
The answer above is entirely correct, I just wanted to point out where I think the misunderstanding comes from. It's a problem in all optical equipment, particularly telescopes.