arcgis 10.0 - How to convert WGS84 to UTM when the study area covers two zones: UTM 51N and 52N

I want to use ArcMap to convert the WGS84 to UTM. But the study area covers two zones: UTM 51N and 52N. Which zone should I choose to output the result?　

Answer

Unless ArcMap prevents you from doing so, take the UTM zone that covers the greater part of your study area.

Alternatively, you can use a Gauss-Kruger CRS based on 126°E, either

EPSG:2676 Pulkovo 1995 3-degree Zone 42

EPSG:2366 Xian 1980 3-degree Zone 42