Bessel Functions

Having just encountered Bessel Functions for the second time in my life, I must say that they did not seem any friendlier. For a non-axisymmetric galaxy gravitational potential (think of a barred spiral galaxy), the surface brightness of the galaxy may be defined using a double integral over two Bessel Functions, J0 and J1, both with different arguments. I have to say, it was gruelling and a pain in the ass, but I was finally able to get it to work out earlier today. It involved doing one integral on the computer, but the rest was a lot of calculus to get it to work. As hard as it was, it was fun, and the satisfaction of actually obtaining a result was great. Still, Bessel Functions and I are not close friends. There are relations between them and various integrals that are easier to do than others, it's just a matter of finding which form you need and how to get there. Rather annoying, but worth the time and effort put in. Maybe I'll post the solution later.