I want to know the answer to the following question:
At long range what, in theory, could be used to set ranging calculations?
All the background I'm provided with is that "At long range, the aircraft remains in firing range for a long time, so the necessary calculations can in theory be done by slide rules - though, because small errors in distance cause large errors in shell fall height and detonation time, exact ranging is crucial.". Is that enough to answer the question?
Answer: yes