diff --git a/pyobs/images/image.py b/pyobs/images/image.py
index 0195620b..c3dc83f7 100644
--- a/pyobs/images/image.py
+++ b/pyobs/images/image.py
@@ -245,7 +245,7 @@ def to_bytes(self) -> bytes:
 
     def write_catalog(self, f: Any, *args: Any, **kwargs: Any) -> None:
         """Write catalog to file object."""
-        if self.catalog is None:
+        if self._catalog is None:
             return
 
         hdu = table_to_hdu(self._catalog)
diff --git a/pyobs/images/processors/_daobackgroundremover.py b/pyobs/images/processors/_daobackgroundremover.py
index 454f4f24..0aa85258 100644
--- a/pyobs/images/processors/_daobackgroundremover.py
+++ b/pyobs/images/processors/_daobackgroundremover.py
@@ -30,7 +30,7 @@ def _estimate_background(self, image: Image) -> npt.NDArray[float]:
             filter_size=self._filter_size,
             sigma_clip=self._sigma_clip,
             bkg_estimator=self._bkg_estimator,
-            mask=image.mask,
+            mask=image.safe_mask,
         )
 
         return bkg.background
diff --git a/pyobs/images/processors/detection/daophot.py b/pyobs/images/processors/detection/daophot.py
index 4f5d5778..fe3feafd 100644
--- a/pyobs/images/processors/detection/daophot.py
+++ b/pyobs/images/processors/detection/daophot.py
@@ -65,7 +65,7 @@ async def __call__(self, image: Image) -> Image:
             Image with attached catalog.
         """
 
-        if image.data is None:
+        if image.safe_data is None:
             log.warning("No data found in image.")
             return image
 
diff --git a/pyobs/images/processors/detection/pysep.py b/pyobs/images/processors/detection/pysep.py
index 2b7cbb45..fc7f084e 100644
--- a/pyobs/images/processors/detection/pysep.py
+++ b/pyobs/images/processors/detection/pysep.py
@@ -23,16 +23,22 @@ class SepSourceDetection(SourceDetection):
     __module__ = "pyobs.images.processors.detection"
 
     _CATALOG_KEYS = [
-        "x", "y",
+        "x",
+        "y",
         "peak",
         "flux",
         "fwhm",
-        "a", "b", "theta",
+        "a",
+        "b",
+        "theta",
         "ellipticity",
         "tnpix",
         "kronrad",
-        "fluxrad25", "fluxrad50", "fluxrad75",
-        "xwin", "ywin",
+        "fluxrad25",
+        "fluxrad50",
+        "fluxrad75",
+        "xwin",
+        "ywin",
     ]
 
     def __init__(
@@ -77,7 +83,7 @@ async def __call__(self, image: Image) -> Image:
             Image with attached catalog.
         """
 
-        if image.data is None:
+        if image.safe_data is None:
             log.warning("No data found in image.")
             return image
 
@@ -104,7 +110,7 @@ async def __call__(self, image: Image) -> Image:
 
     @staticmethod
     def _get_mask_or_default(image: Image) -> np.ndarray:
-        if image.mask is not None:
+        if image.safe_mask is not None:
             return image.mask
 
         return np.zeros(image.data.shape, dtype=bool)
diff --git a/pyobs/images/processors/misc/smooth.py b/pyobs/images/processors/misc/smooth.py
index 7b1a4539..5a1741c4 100644
--- a/pyobs/images/processors/misc/smooth.py
+++ b/pyobs/images/processors/misc/smooth.py
@@ -54,7 +54,7 @@ async def __call__(self, image: Image) -> Image:
         """
 
         output_image = image.copy()
-        if output_image.data is None:
+        if output_image.safe_data is None:
             log.warning("No data found in image.")
             return image
 
diff --git a/pyobs/images/processors/misc/softbin.py b/pyobs/images/processors/misc/softbin.py
index eeb8a9ff..1feb5cea 100644
--- a/pyobs/images/processors/misc/softbin.py
+++ b/pyobs/images/processors/misc/softbin.py
@@ -37,12 +37,12 @@ async def __call__(self, image: Image) -> Image:
         """
 
         output_image = image.copy()
-        if output_image.data is None:
+        if output_image.safe_data is None:
             log.warning("No data found in image.")
             return image
 
         output_image.data = self._reshape_image(output_image.data)
-        if output_image.data is None:
+        if output_image.safe_data is None:
             log.warning("No data found in image after reshaping.")
             return image
 
diff --git a/pyobs/images/processors/offsets/nstar.py b/pyobs/images/processors/offsets/nstar.py
index a56a41e7..371f6132 100644
--- a/pyobs/images/processors/offsets/nstar.py
+++ b/pyobs/images/processors/offsets/nstar.py
@@ -128,12 +128,6 @@ async def _boxes_from_ref(self, image: Image, star_box_size: int) -> List:
         # run pipeline on 1st image
         img = await self.run_pipeline(image)
 
-        # check data and catalog
-        if img.data is None:
-            raise ValueError("No data found in image.")
-        if img.catalog is None:
-            raise ValueError("No catalog found in image.")
-
         # do photometry and get catalog
         sources = self._fits2numpy(img.catalog)
 
@@ -273,7 +267,7 @@ def _calculate_offsets(self, image: Image) -> Tuple[Optional[float], Optional[fl
         """
 
         # data?
-        if image.data is None:
+        if image.safe_data is None:
             return None, None
 
         # calculate offset for each star
diff --git a/pyobs/images/processors/offsets/projected.py b/pyobs/images/processors/offsets/projected.py
index 73cea460..0b457b2b 100644
--- a/pyobs/images/processors/offsets/projected.py
+++ b/pyobs/images/processors/offsets/projected.py
@@ -82,10 +82,6 @@ def _process(self, image: Image) -> Tuple[npt.NDArray[float], npt.NDArray[float]
         # get image data and header
         data, hdr = image.data, image.header
 
-        # no data?
-        if data is None:
-            raise ValueError("Image contains no data.")
-
         # trimsec
         if "TRIMSEC" in hdr:
             m = re.match(r"\[([0-9]+):([0-9]+),([0-9]+):([0-9]+)\]", hdr["TRIMSEC"])
diff --git a/pyobs/images/processors/photometry/pysep.py b/pyobs/images/processors/photometry/pysep.py
index c559ada6..e9afaa9b 100644
--- a/pyobs/images/processors/photometry/pysep.py
+++ b/pyobs/images/processors/photometry/pysep.py
@@ -67,18 +67,15 @@ def _photometry(image: Image) -> Image:
         from pyobs.images.processors.detection import SepSourceDetection
 
         # check data
-        if image.data is None:
+        if image.safe_data is None:
             log.warning("No data found in image.")
             return image
-        if image.catalog is None:
+        if image.safe_catalog is None:
             log.warning("No catalog found in image.")
             return image
 
-        # no mask?
-        mask = image.mask if image.mask is not None else np.ones(image.data.shape, dtype=bool)
-
         # remove background
-        data, bkg = SepSourceDetection.remove_background(image.data, mask)
+        data, bkg = SepSourceDetection.remove_background(image.data, image.safe_mask)
 
         # fetch catalog
         sources = image.catalog.copy()
diff --git a/pyobs/modules/camera/basecamera.py b/pyobs/modules/camera/basecamera.py
index 24640667..96ac0760 100644
--- a/pyobs/modules/camera/basecamera.py
+++ b/pyobs/modules/camera/basecamera.py
@@ -246,7 +246,7 @@ async def __expose(self, exposure_time: float, image_type: ImageType, broadcast:
         self._exposure = ExposureInfo(start=datetime.datetime.utcnow(), exposure_time=exposure_time)
         try:
             image = await self._expose(exposure_time, open_shutter, abort_event=self.expose_abort)
-            if image is None or image.data is None:
+            if image is None or image.safe_data is None:
                 raise exc.GrabImageError("Could not take image.")
 
         except exc.PyObsError:
diff --git a/pyobs/utils/focusseries/projection.py b/pyobs/utils/focusseries/projection.py
index 61e48107..44feb811 100644
--- a/pyobs/utils/focusseries/projection.py
+++ b/pyobs/utils/focusseries/projection.py
@@ -47,7 +47,7 @@ def analyse_image(self, image: Image, focus_value: float) -> None:
         """
 
         # clean data
-        if image.data is None:
+        if image.safe_data is None:
             return
         data = self._clean(image.data)
 
diff --git a/tests/images/processors/test_removebackground.py b/tests/images/processors/test_removebackground.py
index 46981b18..2ecb7d34 100644
--- a/tests/images/processors/test_removebackground.py
+++ b/tests/images/processors/test_removebackground.py
@@ -49,4 +49,4 @@ def test_call_const_background(mocker):
     image = Image(data=np.ones((20, 20)))
     output_image = remover(image)
 
-    np.testing.assert_array_equal(output_image.data, np.zeros((20, 20)))
\ No newline at end of file
+    np.testing.assert_array_equal(output_image.data, np.zeros((20, 20)))
diff --git a/tests/images/test_image.py b/tests/images/test_image.py
index 904f51bf..340931ad 100644
--- a/tests/images/test_image.py
+++ b/tests/images/test_image.py
@@ -24,20 +24,28 @@ def assert_array_equal_or_none(check_value, value):
 
 
 def assert_equal_image_params(image, data=None, mask=None, uncertainty=None, catalog=None, raw=None, meta={}):
-    assert_array_equal_or_none(data, image.data)
-    assert_array_equal_or_none(mask, image.mask)
-    assert_array_equal_or_none(uncertainty, image.uncertainty)
+    assert_array_equal_or_none(data, image.safe_data)
+    assert_array_equal_or_none(mask, image.safe_mask)
+    assert_array_equal_or_none(uncertainty, image.safe_uncertainty)
 
     if catalog is None:
-        assert image.catalog is None
+        assert image.safe_catalog is None
     else:
         assert_array_equal_or_none(catalog.as_array(), image.catalog.as_array())
-    assert_array_equal_or_none(raw, image.raw)
+    assert_array_equal_or_none(raw, image.safe_raw)
     assert image.meta == meta
 
 
 def assert_equal_image(image, other):
-    assert_equal_image_params(image, other.data, other.mask, other.uncertainty, other.catalog, other.raw, other.meta)
+    assert_equal_image_params(
+        image,
+        other.safe_data,
+        other.safe_mask,
+        other.safe_uncertainty,
+        other.safe_catalog,
+        other.safe_raw,
+        other.safe_meta,
+    )
 
 
 @pytest.fixture()