- Open the properties, set the origin manually and then close the properties again to see if you've "hit" the right area, or
- Define the origin as non-absolute, move the lens until you have the right content, open the properties and set the origin to absolute, close the properties and move the lens again.
Instead of the above sequences you would then just create the lens, position it and activate absolute origin, and then just do (e.g.) Ctrl+Drag until it contains the correct image.
Not exactly earth-shaking, but it would be quicker.