Battlestars could deliver a large quantity of firepower in the form of their Viper squadrons, and against Baseships which had lost their Raiders, they were very effective, although at a huge loss in Colonial pilots.
Against Baseships with their Raiders though, the Vipers were outnumbered and they spent their time just keeping the enemy away from the Battlestar, which in itself did not usually have the firepower to destroy the Baseship.
Thus Colonial Command decided that they needed a ship which could take on a Baseship and match it blast for blast and win through superior firepower. Travelling with a Battlestar to provide Viper escort for this new class of ship, the teaming would be an unstoppable force.

And it almost was.

The new ship (The Pulsar Class Gunstar) was almost the size of a Battlestar and while it naturally sacrificed most of its Vipers (carrying only a short squadron of around 60 Vipers), the firepower that it could put out was quite incredible. Carrying one large Mega Pulsar laser, the better of any Cylon Baseship mounted weapon (initially at least), 4 pulsar lasers and two missile launchers, the Gunstar could quite easily destroy any unescorted Baseship on its own, and even give a couple a run for their money.
Against escorted Baseships Pulsar Class Gunstars were also worth their weight in gold. Now the Battlestar and Vipers would engage the Cylon Raiders, and the Gunstar would close in for the kill.

While they can act independently, for any significant length of time they need escort supply and support vessels. During the 1000 yahren war, it was not uncommon to team a Battlestar with a Gunstar. Although commission on a Gunstar was never as glamorous as that of a Battlestar, there were never any shortage of crews for these 'Baseship killers'.

The only flaw was the time it took to build new ones, and thus Pulsar Class Gunstars were only as plentiful as Battlestars, and it was highly unusual to have two serving together in any fleet or squadron. This was mainly due to large pulsar mega-laser mounted near the front of the vessel. As a result of this, several other class of Gunstar were built that sacrificed the pulsar laser for other abilities. The Teucer Class Missilestar and the Spawn Class Fighting Star were examples of these other vessels built on the same hull.

The last Pulsar Class Gunstars were destroyed with the Fifth Fleet.

While they can be as old as Battlestars, the Colonials have never seemed to need a reason to modify these mighty ships, and thus nearly all follow the standard configuration.

Names:

Triton, Bellerophon, Cerberus, Olympia, Valiant, Prometheus, Solaria, Argo, Poseidon, Pulsar

The Gunstar was drawn by Jim Stevenson, SSD's designed by me and drawn by Sean Driscoll.

Pulsar Class Gunstars have two large shuttle bays, and may conduct transfers via (J1.593). Each bay has a launch tube ([J1.54] which will propel a fighter flight to speed 12 and will launch in direction 5 [Alpha bay] or 2 [Beta bay]) and a standard shuttle hatch (launching and landing from direction 4 for both bays).
The shuttle bays are large enough to accept yachts.
The Gunstar has a hyperspeed multiplier of x1.

Colonial Pulsar Class Gunstar boarding diagram:

Master Ship Chart Extract:

Annex #7B: Ships able to land on planets

This ship may not land on a planet.

Annex #7G: Carrier information & Annex #7N: Missile reloads