Before the Battlestar Pegasus arrives, the Galactica reads a total of four Basestars engaging them. When the Pegasus arrives, only three are shown attacking the Galactica. After the Pegasus destroys one, the Dradis screen is shown to the audience displaying again four Basestars.
(at around 57 mins) While Baltar is advising the Cylons to leave New Caprica, the camera circles round his shoulder to show the green screen outside Colonial 1's porthole.
Pegasus' main bow batteries are deleted, and it appears that Pegasus only has the turret batteries firing.