I am trying to show a single sphere at c-alpha carbons for some point mutants that i designed. When I use the command:
show /a:473,476,477 atoms
I can see all the atoms in chain A for residues 473, 476, 477.
Using: show /a:473,476,477@cb atoms
I can show "two spheres" for the c-alpha and c-beta carbon.
When I use:
show /a:473,476,477@ca atoms nothing happens and i don't see any spheres.

If I show the full atom and then do:
hide /a:473,476,477@ca* atoms

Just the c-alpha sphere gets hidden. 

Why is it that i can't just show the c-alpha spheres? Unfortunately for my figure i make silhouettes of my model and so i can't just hide the other atoms by making them fully transparent