Update viewer tutorial
@@ -311,7 +311,7 @@ viewer.add_image(blobs, name='blobs', opacity=0.5, colormap='red')
```{code-cell} python
:tags: [hide-input]
-nbscreenshot(viewer, alt_text=" ")
+nbscreenshot(viewer, alt_text="A 2d view of the moon on top of which is overlaid a 3d volume containing blobs through which you can navigate using the dimension slider.")
```
In order to get or to update the current position of the slider, use
