Davies, make sure you have decent weapons and systems (I forget what Mk equipment captains have) and, for the Galaxy class; I can only suggest what I used, 2 photons and 2 beams at the front, the back is either 2 photons and 1 beam, or the other way around, depending on your play style.
If this Keldon uses the photonic fleet attack (suddenly, 3 more enemies appear) keep hitting the Keldon, as soon as it dies, the other ships simply dissappear.
Any other info would be nice though (Engineer? Tactical? Science? BO abilities?)