Cheapest way to piggyback SLR for astrophotography?

[mbaddah]

Title pretty much says it all, am wondering what would be the cheapest way tp piggyback an SLR for some basic long-exposure astrophotography? I know there is the barn-door solution but im terrible at woodwork :( Cheers.

[iceman]

You'll really still want a good solid mount, a refractor for guiding, with rings and a bar on top to put your tripod-head and camera on.