Red Line
For information on the Freespace 2 conversion mod, see Beyond the Red Line

The Red Line is an imaginary sphere enclosing a vessel which denotes the maximum safe limit for an FTL jump.^{[1]} It is described in an early draft of the script for the Miniseries as follows:
 "There are computational errors in every jump. The further out you jump, the greater the error. Jump past the Red Line and it may be almost impossible to find your way back."
And in the series bible^{[2]} as follows:
 "Practically speaking the further one attempts to Jump, the more difficult the calculations and the more variables are introduces into the equations. For example, consider the difficulties inherent in Jumping to a relatively nearby star system "only" five light years away: any information Galactica can gather by looking through a telescope is, by definition, five years old. The star and all the planets surrounding it have been in motion for five years since the light we can see left that system. This means that Galactica must calculate the motion of all the celestial bodies in that system based on information that is five years old. The further away the Jump point, the greater the problem  try to jump 100 light years, and you have a century's worth of calculations to do.
 Because of the limitations inherent in colonial technology, their ability to calculate all the variables involved in a Jump are also limited. Their margin of error increases exponentially the further out they go and as a result, there is a theoretical "Red Line" beyond which it is not considered safe to attempt to Jump."
This is the issue faced by Raptor 718 after it jumps away from its position near Earth, as they discover that they have jumped beyond the Red Line and are unable to jump back to their previous coordinates (TRS: "The Face of the Enemy").
Jump Limitations
Jump limits are most likely the result of a combination of factors including:
 The computational power available for jump calculations.
 Local gravitational forces (such as nearby planets, stars etc.) which must be compensated for at either end of the jump.
 The accuracy and detail of data concerning the emergence zone at the far end of the jump.
It is possible to exceed this limit, but there is no guarantee as to the accuracy of jump plots beyond that point. A ship could easily materialize within a stellar body or end up far off course.
When attempting to escape the Cylons after their devastating attack on the Twelve Colonies, and with the future of 50,000 survivors on his hands, Commander Adama orders a jump "beyond the Red Line" to the Prolmar Sector. Given the nature of Colonial technology and vessels, it is probable this particular limit reflects the overall capabilities of the Fleet as a whole, and not just Galactica itself.
Cylon FTL jump technology is more advanced than Colonial technology. As such, an equivalent distance to the Colonial Red Line plotted with a Cylon navigational computer (from the small Raider to the gargantuan basestar) has a much smaller margin of error, enabling the Cylons to accurately plot jumps for much longer distances. While the actual distance between Kobol and Caprica is not specified, Kara Thrace is able to take a captured Raider from the vicinity of Kobol to Caprica in a single jump (TRS: "Kobol's Last Gleaming, Part I").
The range advantage of the Cylon FTL systems however, does not lie within the drive units themselves, but the navigational computers used to calculate the jump plots. When installed aboard a Colonial Raptor, the computer from a captured Heavy Raider enables the vessel to increase its jump distance by a factor greater than ten (TRS: "Lay Down Your Burdens, Part I").
References
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