Drywall anchor pull-out strength
I would only trust a toggle bolt type anchor in a ceiling or overhead application, even if the manufacturer's information shows an auger or plastic expansion type anchor is strong enough.  With augers or plastic anchors, if the hole is just a little sloppy, the holding power is dramatically reduced.  

The table below shows that even the smallest toggle in the thinnest drywall has a tension rating of 115 pounds, so at the recommended safety factor of 4x, it can support almost 29 pounds.  

I would locate the nearest joists with a stud finder, just to see if there's one that's close enough to the spot;  if not, I'd use a 3/16" or 1/4" toggle.  I'd recommend a Strap-Toggle, Snaptoggle or similar, they are quite a bit easier to work with than traditional toggles, especially overhead.