Sorry, I�m not sure what to suggest. Everything in Quick Base needs to have a form of Authentication, so I don't know how you would do that unless someone writes some kind of script to execute when that Sharepoint webpage loads.
If you are willing to push a button there is code to Authenticate and then redirect to display the chart when a button is pushed. You would need to se up a dedicated userid with limited permissions, for that as the userid and password would likely be exposed in the URL address bar, so not secret at all.