I was wandering, if anyone ever attempted to build coma corrector or FF from surplus optical parts (for example, it should be possible to build the meniscus from elements from air spaced achromatic objective lenses).
I found some links on the web, like this one:
http://scopes.wikispaces.com/Two+Element+Coma+Corrector
I will certainly try it myself.. and any previous experiences would be helpful and much appreciated (but they won't to stop me from coming to my own conclusions about futility of the effort

)