When baking a pie in an aluminum or other metal pie pan it can be hard to tell if the bottom of the pie is done.
However if you really want to be able to see if the bottom of the pie is done you should bake your pies in a glass see through pie baking dish.
I used to bake pies in a non see through pie pan and it was hard to tell when the bottom of the pie was done but after using a see through glass pie baking pan I can now see the bottom of the pie to ensure it's fully cooked.
However if you don't have a see through pie baking dish then you can usually tell when the bottom of the pie is done or any other part of the pie is done when it's bubbling for 6 to 10 minutes.
A pie is usually fully cooked and done and the bottom of the pie is usually fulled cooked if the crust is brown and the filling is bubbling for 6 to 10 minutes.
Depending on the type and size of the pie it takes between 45 minutes to 1 hour to bake most pies.