Any guide star can be brought between the lines of the built-in micrometer scale by simply rotating the eyepiece - only then can the many off-axis systems in existence become really useful tools for astrophotography.
Using double reticule eyepieces or eyepieces with a simple reticule you are often forced to blur the guide star so that it does not suddenly disappear behind the thick reticule lines leading to complete failure - immediately costing you 2 magnitudes.
The fine etching of the micro guide eyepiece micrometer scale means you can safely keep sharply focused stars between the lines, allowing you to use much fainter stars as guide stars.
