📝 Improve documentation

README.md

@@ -33,6 +33,30 @@ aladin = Aladin()
 aladin
 ```
 
+## Widget limitations
+
+Because some limitations of the widget framework, some operations need specific behaviors.
+
+### Aladin Lite values
+
+Some values need to be synchronized before their use, like:
+
+- wcs
+
+#### Example with the wcs value:
+
+First cell:
+
+```python
+aladin.synchronize_wcs()
+```
+
+Second cell:
+
+```python
+print(aladin.wcs)
+```
+
 ## Development installation
 
 First, make sure you have installed jupyter in your python environnement: `pip install jupyter`.

src/ipyaladin/aladin.py

@@ -199,8 +199,8 @@ def wcs(self) -> WCS:
         """
         if self._wcs == {}:
             raise ValueError(
-                "You need to call synchronize_wcs first and in "
-                "another Jupyter cell to get the WCS."
+                "You need to call synchronize_wcs before accessing the wcs attribute. "
+                "The WCS attribute need to be accessed from the next cell."
             )
         wcs = WCS(naxis=self._wcs["NAXIS"])
         wcs.wcs.cdelt = [self._wcs["CDELT1"], self._wcs["CDELT2"]]