Temperature of tandoor for making naan
There isn't much detailed information for this online.  Even the various manufacturers don't generally cite desired temperatures.  Wikipedia says up to 480C/900F, but does not cite a source for this temperature.  The NY Times says that a traditional charcoal tandoor gets up to 750F, but does not mention a source either.  Homedoor, the one manufacturer who mentions a temperature, says that their units go up to 650F.  

None of these sources mention a desired optimal temperature, though.  It seems likely that the temperature would be similar to the optimal temperature for Neopolitan pizza, between 600F and 700F.

Also, a tandoor is designed so that the clay walls will be hotter than the air inside the oven -- I'd assume probably 50-100F hotter, but that's basically a blind guess as I can't find any measurements anywhere.  

The one thing I can tell you from personal experience is that you cannot make Indian naan with the proper texture in a home oven with a pizza stone which only gets up to 525F.  Believe me, I've tried.

Links:


http://en.wikipedia.org/wiki/Tandoor
http://www.nytimes.com/2011/05/11/dining/a-tandoor-oven-brings-indias-heat-to-the-backyard.html?pagewanted=2&amp;_r=1
https://homdoor.com/index.php/home/