The only limit to field stop size is the inside diameter of the eyepiece’s barrel. So, for example, a 20mm 2″ eyepiece will show more sky than a 20mm 1¼” eyepiece through the same telescope. What’s more, the magnification through both eyepieces will be the same.
Most observers prefer a wider field that doesn’t sacrifice higher magnification. This really helps skywatchers whose telescopes lack a motorized drive. A wider true field of view means you have to manually move your scope less often to follow objects as Earth rotates. — Michael E. Bakich, Senior Editor