Dex Nav shiny odds?/ Does Shiny charm increase odds?

[OGaryOak]

Replying through orAS at the moment b4 next gen release 
with my first legit SR shiny starter 
Male Torchic nicknamed : FireFox  
i love him so much :D


was wondering is dexnav odds a static 1/512 chance for shiny ?? 

and does shiny charm increase those odds at all ?

ive done quite a bit of dexnav hunting for shinies on orAS
but alway had the charm before i cleared game file so just wondering?


thanks in advance for your responses!