I finally got hold of a different set of constants, and I'm happy to say that the converter is now scientifically accurate. Given the RA/Dec from an official star catalog, it produces the same galactic coordinates that the catalog shows :D
The error before was small, yes, but it irked me to no end.
Also, I discovered a grievous error in the conversion to cartesian coordinates. That is now working correctly as well, with X being the vector towards the galactic center, Y being the spinward vector, and Z being the vertical vector.

As this is an important bugfix, I hope it'll find its way to the archives soon :)

Laura, I believe you now have the longest "hello" thread ever on the boards. I'm very glad to see you not only found us, but so quickly jumped in and are contributing.

lol, yes.. it's a long one. But I figured since the development of the converter application has been discussed mainly here, it was best to keep it here :)