Black family names (astronomy)

[Blaise]

Catlady wrote: Rastaban is beta Draconis. Was that the name of 
Rodolphus Lestrange's brother (the fourth man of the Pensieve Four)?

Monika said yes to this, but in my version of OotP Rodolphus' brother 
is called Rabastan, not Rastaban. I can't find Rabastan in my little 
star dictionary, nor in my classical dictionary. Can anyone enlighten 
me as to what the name signifies? Or did JKR mean Rastaban and make 
an error? Or is it just my copy of OotP?

As for Narcissus, as far as I know there is no star or constellation 
with this name, nor is there any connection between the myth of 
Narcissus and the stars. So I conclude that JKR chose Narcissa as a 
name to represent the woman's qualities rather than following the 
Black family tradition. I suppose one could think up some kind of 
backstory concerning Narcissa Black's birth and childhood that 
explains why she was given a non-astronomical name (could she be a 
bastard child? or her mother had her in a previous marriage?). Any 
other theories?

I hope everyone who went enjoyed Nimbus! Wish I'd been there!

Blaise