always more complicated

Heard from Dave L regarding the offset mystery with BGO and the SBIG. I was getting big jumps (and then gaps) in the vertical parameter.

In looking at the code, it is more complicated...  It [appears] it does not consider the actual field size (fullsize=yes or no).  I'll look into this in detail and likely make it smarter and update the docs with what it actually does. 

So I'm not going crazy. It's the robot that's crazy.