Let us not forget that many of the professionals at one time was a hobbyist. There are no exact line between the two. I like  the term serious better. You are serious in your work, you are serious of your hobby. Before I made very good money in the software construction business, but before that I was a 'hobbyist' programmer for three years. A hobbyist that worked 60 hours a week and often more, a hobbyist that was more serious than many professionals. So let us have no prejudices. If you have a hobby, why not take it seriously?