BA said here ( http://www.badastronomy.com/bablog/2...#comment-96235 ): "But I also worked very hard on trying to extract an object’s spectrum from its parent star’s spectrum, and we spent weeks on it, and eventually gave up. It was impossible due to scattered light. That was heartbreaking."

Ok maybe it's a little (very) specific, but what is scattered light, and why does it make it hard to get a good spectrum?

Thank you.