How do I take a screenshot in iOS without hitting the Home Button and the Power Button? I would like to take a picture of this Apple Pay popup, while TouchID is active. However this seems impossible to do, since the TouchID sensor is also the home button, which prevents a screenshot from being taken. 

Is there any alternative to taking a screen shot?
You could enable AssistiveTouch in Settings > General > Accessibility and then clicking on it's icon, and tapping Device > Take Screenshot.