diff --git a/common/src/aaredaqlib/diffraction_geometry.py b/common/src/aaredaqlib/diffraction_geometry.py
index ffbcead3..3a1f1219 100644
--- a/common/src/aaredaqlib/diffraction_geometry.py
+++ b/common/src/aaredaqlib/diffraction_geometry.py
@@ -36,7 +36,7 @@ class DiffractionGeometry(BaseModel):
         if exp_dtz_mm <= 0:
             raise ValueError("Detector distance must be positive")
 
-        theta = math.atan(self.detector_radius_mm / exp_dtz_mm) / 2.0
+        theta = math.atan(self.detector_radius_mm / exp_dtz_mm)
         return self.wavelength_angstrom / (2 * math.sin(theta))
 
     def calc_dtz_mm(self, exp_resolution_angstrom: float) -> float:
@@ -44,4 +44,4 @@ class DiffractionGeometry(BaseModel):
             raise ValueError("Resolution must be positive")
 
         theta = math.asin(self.wavelength_angstrom / (2 * exp_resolution_angstrom))
-        return self.detector_radius_mm / math.tan(2 * theta)
\ No newline at end of file
+        return self.detector_radius_mm / math.tan(theta)
\ No newline at end of file