diff --git a/pyobs/mixins/fitsheader.py b/pyobs/mixins/fitsheader.py
index 9c567b00..2dd3ab78 100644
--- a/pyobs/mixins/fitsheader.py
+++ b/pyobs/mixins/fitsheader.py
@@ -348,8 +348,14 @@ def v(k: str) -> Any:
 
             # PC matrix: rotation only, shift comes from CDELT1/2
             if self._fitsheadermixin_rotation is not None:
-                hdr["POSANG"] = (self._fitsheadermixin_rotation, "Position angle [deg e of n]")
-                theta_rad = math.radians(self._fitsheadermixin_rotation)
+                # position angle is set rotation + DEROTOFF if defined
+                posang = self._fitsheadermixin_rotation
+                if "DEROTOFF" in hdr:
+                    posang += hdr["DEROTOFF"]
+
+                # write position angle
+                hdr["POSANG"] = (posang, "Position angle [deg e of n]")
+                theta_rad = math.radians(posang)
                 cos_theta = math.cos(theta_rad)
                 sin_theta = math.sin(theta_rad)
                 hdr["PC1_1"] = (+cos_theta, "Partial of first axis coordinate w.r.t. x")
diff --git a/pyproject.toml b/pyproject.toml
index b62b1b8f..c4ee201e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,7 +1,7 @@
 [tool.poetry]
 name = "pyobs-core"
 packages = [{ include = "pyobs" }]
-version = "1.6.8"
+version = "1.6.9"
 description = "robotic telescope software"
 authors = ["Tim-Oliver Husser <thusser@uni-goettingen.de>"]
 license = "MIT"