Please read the specifications carefully:
Angular range: 1600 seconds (±600 seconds calibrated) *
Best Accuracy: 0.2 seconds
System Accuracy: ±1 seconds over central 100 seconds, ±6 seconds over ±600 seconds
Where is best accuracy achived, at zero point?
System accuracy is ±1" (±4.85µm/m or ±0.00028°) over ±50" (±242,41µm/m or ±0,01389°) that means a five times worse accuracy near zero point and ±6" (±29.09µm/m or ±0,00167°) over ±600" (2908,87µm/m or 0.16667°). That is not as amazing as it seems at first glance. If you compare that with a Wyler Zerotronic ±0.5° the Wyler is the winner.
-branadic-