While I was wandering around the net this morning, I came across this site that has all the "Telescope Making" mags on pdf. As I'm researching things to do with my 350mm f/4.3 mirror, I took the time to go through all the contents of "Telescope Making" and found an article of building coma correctors using off the shelf optics. I have no idea of the article contents as you have to buy the issue ($US3.95) to read it. However here it is.
http://www.kalmbachstore.com/tmkpdf045.html