Blaschke product+asymptotic

I have the following question related to Blashke product:

B_n(u) = product_{k=1}^n (u - a_k_)/(1-\bar{a_k}*u) -

usual Blashke product.

I have the a_k = r e^{2pi * i /n}, a_k - are vertices of a regular n-gon on the cirlcle of radius r.

Is there any asympotic relations(formula) for B_n(u) when
n -> infty.

Maybe some of specialist can give some references to the facts related to the behaviour of Blashke product when the number of poles tends to infinity.

Thanks
.