How to identify where studs are from outside wall?

[Jamesrg]

I tried to put an awning up over this door, but where the holes lined up there isn't enough support.
I tried using toggle type of bolt but couldn't get it secure enough.
In the picture you can see where I tired this.
How do I identify where the studs are so I can anchor into them?

 

[Paul Cumbria]

It might be worth considering the use of chemical anchors here. Most builder's suppliers stock them, and the staff can advise on the type to use and how to use them correctly. I have used them in various locations and they are rock solid.

 

[MikeShutt]

There should be king studs just an inch or two further out than where the holes are. You can verify from inside the house using a stud finder (or hammering a small nail through the drywall).