What you pronounce “o” or “a” depends on where you live. It’s ok to pronounce “o” in the northern part (as well in Ukraine and Belarus) and “a” in the southern part of Russia. That's why I think it is quite possible to hear “o” in Novgorod. It is “proper” to pronounce “a” in the places where I lived – Vladivostok, St. Petersburg and Moscow. I think most of the Russians pronounce “a”.

What do you mean about "оканнье"?

They are say "a", but you hearing it like "o"... It's only seem... Они говорят "а", а слышится "о". Это только так кажется...

I'm a native speaker of Russian and I use "аканье", I don't know anybody who uses "оканье".

I don't think we may speak of a "correct" pronunciation !!! But if you seek someone without dialectic influence, go to the Russian Far East. In this regard the language is cleanest there (where I live) ^__^ Though modern linguists say that even in the Far East region today people are already pronouncing vowels a bit differently...