Hey Guys

Sorry for being a total newbie but I have spent several hours looking around the internet for information on how to work out these values and I simply cant find how.

I have a delta printer (Kickstarter kit) running Repetier firmware. It has an optical assisted calibration feature however after sever hours of running and re-running the calibration routine the calibration values are all over the place and not consistent.
Therefore I would like to do the good ole paper style calibration using the manual scripts and Repetier. However I need to write the scripts to get the nozzle to the middle of each tower just above the bead.
How do I work out these X, Y + Z co-ordinate values?

Every post/thread/website I read mentions the values and what to do to adjust the firmware to suit either concave or convex movement. I am yet to find somewhere that tells me how to actually work the values out.
I dont know the measurements of the printer off hand but I do have a CAD file of the printer which I can measure from if that helps?

Any help greatly appreciated.

Thanks