F-14 in the sights of, what I believe to be, an A-4 Skyhawk during a DACT (Dissimilar Air Combat Training) mission.
I say it might be a Skyhawk because they featured a distinct set of aiming circles as explained in the following picture:
The A-4’s gunsight, shown here centered by a Top Gun aggressor on the A-4 of his flight leader, places the pilot at a disadvantage in a gun attack. Only one generation removed from World War II gunsights, it has no radar to calculate lead - how far ahead of a turning adversary to aim. As a poor substitute, it displays a set of aiming circles that offer the pilot minimal assistance in judging lead, which he must then dial manually into the gunsight.