Add criteria to restrict queried table size

python/lsst/ts/observatory/control/base_tcs.py

@@ -27,6 +27,7 @@
 import logging
 import typing
 import warnings
+from functools import partial
 from os.path import splitext
 
 import astropy.units as u
@@ -1687,43 +1688,40 @@ async def find_target_simbad(
 
         radec = self.radec_from_azel(az=az, el=el)
 
+        # Build the ADQL-like criteria for V magnitude + HD catalog
+        criteria = (
+            f"V>{mag_limit} AND V<{mag_limit + mag_range} " f"AND main_id LIKE 'HD%'"
+        )
+
+        query_callable = partial(
+            customSimbad.query_region,
+            coordinates=radec,
+            radius=radius * u.deg,
+            criteria=criteria,
+        )
+
         # Execute the query_region asynchrnously
         loop = asyncio.get_event_loop()
         try:
-            result_table = await loop.run_in_executor(
-                None, customSimbad.query_region, radec, radius * u.deg
-            )
+            result_table = await loop.run_in_executor(None, query_callable)
         except Exception as e:
             self.log.exception("Querying Simbad failed.")
             raise RuntimeError(f"Query region for {radec} failed: {e!r}")
 
         if result_table is None or len(result_table) == 0:
             raise RuntimeError(f"No results found for region around {radec}.")
 
-        # Filter by V magnitude
-        good_mag = (result_table["V"] > mag_limit) & (
-            result_table["V"] < (mag_limit + mag_range)
-        )
-        result_table = result_table[good_mag]
-
-        # Further filter for HD objects (prefix "HD")
-        hd_mask = [str(name).startswith("HD") for name in result_table["main_id"]]
-        result_table = result_table[hd_mask]
-
-        if len(result_table) == 0:
-            raise RuntimeError(
-                f"No 'HD' object in Simbad catalog with magnitude between"
-                f" {mag_limit} and {mag_limit+mag_range}."
-            )
-
         # Sort by V magnitude
         result_table.sort("V")
-        target_main_id = str(result_table["main_id"][0]).strip()
+
+        # Pick the first (brightest) match
+        target_main_id = str(result_table["main_id"][0])
 
         radec_icrs = ICRS(
             ra=Angle(result_table[0]["ra"], unit=u.deg),
             dec=Angle(result_table[0]["dec"], unit=u.deg),
         )
+
         self.object_list_add(f"{target_main_id}".rstrip(), radec_icrs)
 
         return f"{target_main_id}".rstrip()