Hi
Stepper motors are usually limited in what they can do. They don't have the speed range of the more common electric motors with encoders. If you make the steps small enough for smooth tracking the slew speed will probably not be fast enough for satellites although they can be quite precise in their positioning.
There was a stepper motor drive system quite popular 12 years ago called the DOB 11 driver system or Roboscope. Used for driving Dobsonian mounts I believe they are still available but quite expensive. I had one and did a lot of experimenting with it until I got a LX200 which was far superior in its control.
I wrote a program in Qbasic to drive it complete with goto, two star alignment and catalogues of ngc, IC an Messier objects and a selection of stars for alignment. The method of imparting drive to the axes was by belts or friction drive and was suseptible to slipping. I also had a version of this program that used to drive stepper motors salvaged from old hard MFM drives. I found one variety that would accept up to 3000 half-steps/sec from a stepper drive PC board kit from Silicon Chip. Incidently the steppers that came with the DOB 11 ran at up to 5000 half-steps/sec.
I am not very familiar with the Argo Narvis system but If you put decent ball or roller bearings with some preload on all the rotating sections and a positive method of drive by toothed belts or gears I think it will turn out more practical and cheaper in the long run.
On my web site there is some old files of the work I did years ago in beefing up a Dobsonian Mount and fitting of a DOB 11
Barry
www.geocities.com/barrykgerdes
PS. By the way the plural of axis is axes