Ewan,
Yes,
That crescent is a sort of count down final range which gave you some idea of how much further you needed to go...Notice that it has shortened by several divisions before the left missile gets its "Range Bracket" followed by the right missile. Can't now remember the name of the missile, but it had a heat seeking arial inside transparent windows in its nose. If you walked past it with a lighted cigarette then you would see it lock on to it...Anyway, for that missile you would not expect the range brackets to show till that range arc had shortened some.
Easy of use? ...Well the Pilot Attack Sight was instinctive and dead simple to use at the very end of the attack. However, the radar control handle with all its buttons, triggers and wheels required considerable learning and the whole attack was planned and executed by the pilot using this. It was not easy and the simulator was used a lot for training. I was a Lightning Simulator Instructor at Leconfield...The sim was the Mk2.
Here are a couple of shots of the Sim:-
The instructor in the first shot is Dave Trick. That is my TACAN wheel tucked up against the windscreen on the left of the cockpit.