Add an example use of the angle TrajectoryExplorer to notebook

notebooks/TrajectoryExplorer.ipynb

@@ -160,6 +160,45 @@
     "            axs[i, j].imshow(result.all_stamps[ind], cmap=\"gray\")"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Using (RA, dec)\n",
+    "\n",
+    "You can also use the `TrajectoryExplorer` with a WCS and (RA, dec) coordinates. Both RA and dec are specified in degrees and the corresponding velocities are expressed as degrees per day.\n",
+    "\n",
+    "We start by creating a fake WCS to match our fake images. Then we evaluate the trajectory based on this WCS."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from astropy.wcs import WCS\n",
+    "\n",
+    "my_wcs = WCS(naxis=2)\n",
+    "my_wcs.wcs.crpix = [201.0, 251.0]  # Reference point on the image (center of the image 1-indexed)\n",
+    "my_wcs.wcs.crval = [45.0, -15.0]  # Reference pointing on the sky\n",
+    "my_wcs.wcs.cdelt = [0.1, 0.1]  # Pixel step size\n",
+    "my_wcs.wcs.ctype = [\"RA---TAN-SIP\", \"DEC--TAN-SIP\"]\n",
+    "\n",
+    "# Use the WCS to compute the angular coordinates of the inserted object at two times.\n",
+    "sky_pos0 = my_wcs.pixel_to_world(50, 60)\n",
+    "sky_pos1 = my_wcs.pixel_to_world(55, 58)\n",
+    "\n",
+    "ra0 = sky_pos0.ra.deg\n",
+    "dec0 = sky_pos0.dec.deg\n",
+    "v_ra = sky_pos1.ra.deg - ra0\n",
+    "v_dec = sky_pos1.dec.deg - dec0\n",
+    "print(f\"Object starts at ({ra0}, {dec0}) with velocity ({v_ra}, {v_dec}).\")\n",
+    "\n",
+    "result = explorer.evaluate_angle_trajectory(ra0, dec0, v_ra, v_dec, my_wcs)\n",
+    "print(result.trajectory)"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},
@@ -178,13 +217,20 @@
     "explorer.apply_sigma_g(result)\n",
     "print(f\"Valid time steps={result.valid_indices}\")"
    ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
   }
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python (.conda-kbmod)",
+   "display_name": "Jeremy's KBMOD",
    "language": "python",
-   "name": "conda-env-.conda-kbmod-py"
+   "name": "kbmod_jk"
   },
   "language_info": {
    "codemirror_mode": {
@@ -196,7 +242,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.12.1"
+   "version": "3.12.2"
   }
  },
  "nbformat": 4,

src/kbmod/trajectory_utils.py

@@ -13,6 +13,7 @@
 
 import numpy as np
 
+from astropy.coordinates import SkyCoord
 from astropy.wcs import WCS
 from yaml import dump, safe_load