corr typo => improve err msgs

Sim/Scan/AlphaScan.cpp

@@ -128,13 +128,12 @@ CoordSystem1D* AlphaScan::scanCoordSystem() const
 void AlphaScan::checkInitialization()
 {
     if (wavelength() <= 0.0)
-        throw std::runtime_error(
-            "Error in AlphaScan::checkInitialization: wavelength shell be positive");
+        throw std::runtime_error("AlphaScan called with invalid wavelength: is not > 0");
 
     const std::vector<double> axis_values = m_axis->binCenters();
     if (!std::is_sorted(axis_values.begin(), axis_values.end()))
-        throw std::runtime_error("Error in AlphaScan::checkInitialization: q-vector values "
-                                 "shall be sorted in ascending order.");
+        throw std::runtime_error("AlphaScan called with invalid alpha_i vector:"
+                                 " is not sorted in ascending order");
 
     // TODO: check for inclination angle limits after switching to pointwise resolution.
 }