The Taris Orange Mastery Datacron is located in the The Brell Sediment map on Taris grants Mastery +4 (it used to grant Cunning +4 before the stats changed).
The closest Imperial quick travel point is the Bomber Command Post quick travel point and the closest taxi is the Bomber Command Post Speeder speeder point, both in the bottom of the map.
The Taris Orange datacron is in the Abandoned Pirate Cave and is only available to Imperial characters (Republic players must make an Imperial character to unlock this datacron). Finding this datacron will give you a permanent stat boost of Mastery +4 to all your characters on your server, and will unlock the Galactic History 52: Exar Kun Faces Korriban codex.
Taris Mastery +4 Datacron (Imperial)
Quicktravel: Bomber Command Post
Taxi: Bomber Command Post Speeder
Location: The Brell Sediment - Abandoned Pirate Cave
Difficulty: Very Hard - Lots of jumping
Codex: Galactic History 52: Exar Kun Faces Korriban
How to Get the Taris Orange Mastery Datacron
Quick Travel / Taxi
Bomber Command Post
Find the Abandoned Pirates Caves
Take the Elevator Down
Find the Load Lifter
Jump from the loadlifter, to the shelf with boxes, onto the tallest box, to the rounded pipe, to the taller shelves with boxes, to a pile of boxes, to a shipping crate’s edge that’s sticking out, onto the little notch in the shipping crate, onto the shipping crate, onto another pile of boxes, across a big gap with a running jump to a shipping crate, onto another pile of boxes, a careful diagonal jump onto a thin metal pipe, a running jump across some metal shelves, a running jump to another shipping crate while ignoring the boxes on the right, and then a little jump down onto the yellow datacron on a shelf. Got it?