I am currently finishing a german equatorial mount for a 12" telescope. I have planned to use it for some astrophotography when finished. I have little access to litterature on making such a mount. The R.A. shaft will be joined to the DEC. tube by welding (probably). I have a 45 cm (18") R.A. shaft. The problem is - how much deviation from the perpendicular is acceptable - considering it is to be used for astrophotography? Is 1 mm at the end of the R.A. shaft too much/too strict? What value would be practical to go for (in mm or deg.)?
Bjørn