added dm.query_rc to doc

doc/source/ch08_csst_common.rst

@@ -65,39 +65,55 @@ You will get the outputs:
     In your local development environment, you have to use
     ``CsstMsDataManager.from_dir(...)`` to initialize it.
 
+Attributes
+^^^^^^^^^^
+
 Some attributes can be accessed as below.
 
 .. code-block:: python
 
     # access L0 directory
-    dm_mbi.dir_l0
+    dm.dir_l0
     # access L1 directory
-    dm_mbi.dir_l1
+    dm.dir_l1
     # access dir_pcref
-    dm_mbi.dir_pcref
+    dm.dir_pcref
     # access path_aux
-    dm_mbi.path_aux
+    dm.path_aux
     # access ver_sim
-    dm_mbi.ver_sim
+    dm.ver_sim
     # access target detectors
-    dm_mbi.target_detectors
+    dm.target_detectors
     # access available detectors
-    dm_mbi.available_detectors
+    dm.available_detectors
     # define an L1 file (detector-specified)
-    dm_mbi.l1_detector(detector=6)
+    dm.l1_detector(detector=6)
     # define an L1 file (non-detector-specified)
-    dm_mbi.l1_file("flipped_image.fits")
+    dm.l1_file("flipped_image.fits")
 
 To get master files:
 
 .. code-block:: python
 
     # to get bias
-    dm_mbi.get_bias()
+    dm.get_bias()
     # to get dark
-    dm_mbi.get_dark()
+    dm.get_dark()
     # to get flat
-    dm_mbi.get_flat()
+    dm.get_flat()
+
+Query Reference Catalog
+^^^^^^^^^^^^^^^^^^^^^^^
+
+``CsstMsDataManager`` provides a method ``query_rc`` to query reference catalog from ``DFS``.
+
+.. code-block:: python
+
+    cat = dm.query_rc(ra=180, dec=0, radius=2, min_mag=0, max_mag=30)
+    if cat is None:
+        print("The query failed!")
+    else:
+        print("The query succeeded!")
 
 
 Access code to data products