diff --git a/docs/source/images/dtool_dark.png b/docs/source/images/dtool_dark.png
index 4bdeafe1..0b630fd7 100644
Binary files a/docs/source/images/dtool_dark.png and b/docs/source/images/dtool_dark.png differ
diff --git a/docs/source/images/dtool_light.png b/docs/source/images/dtool_light.png
index b4d0c163..8d6226a8 100644
Binary files a/docs/source/images/dtool_light.png and b/docs/source/images/dtool_light.png differ
diff --git a/docs/source/user-guide/filtering.ipynb b/docs/source/user-guide/filtering.ipynb
index 47a7e7d7..b6dd38b7 100644
--- a/docs/source/user-guide/filtering.ipynb
+++ b/docs/source/user-guide/filtering.ipynb
@@ -43,7 +43,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 5,
    "id": "3ac5bc3b",
    "metadata": {},
    "outputs": [],
@@ -150,12 +150,14 @@
    "metadata": {},
    "outputs": [],
    "source": [
+    "import erlab.analysis as era\n",
+    "\n",
     "from erlab.io.exampledata import generate_data_angles\n",
     "\n",
     "cut = generate_data_angles(\n",
     "    shape=(500, 1, 500),\n",
     "    angrange={\"alpha\": (-5, 5), \"beta\": (-10, 10)},\n",
-    "    temp=50.0,\n",
+    "    temp=200.0,\n",
     "    seed=1,\n",
     "    bandshift=-0.15,\n",
     "    Simag=0.1,\n",
@@ -189,9 +191,9 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "result = era.image.curvature(cut, a0=1.0, factor=1.0)\n",
+    "result = era.image.curvature(cut, a0=0.1, factor=1.0)\n",
     "\n",
-    "result.qplot(vmax=0, cmap=\"Greys_r\")"
+    "result.qplot(vmax=0, vmin=-200, cmap=\"Greys_r\")"
    ]
   },
   {
@@ -297,7 +299,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3 (ipykernel)",
+   "display_name": "erlab",
    "language": "python",
    "name": "python3"
   },
@@ -311,7 +313,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.12.6"
+   "version": "3.12.7"
   }
  },
  "nbformat": 4,