Would someone know of a good reference on the oldest known predictions of constellation positions?

How far ahead could accurate positions be predicted?

For example, could current constellation positions be accurately predicted between A.D. 69 to A.D. 86?

  • 1
    $\begingroup$ Constellations wouldn't change that much in such a short time period... Unless one of the stars went supernova. $\endgroup$
    – user10106
    Sep 22, 2017 at 13:30
  • $\begingroup$ How about the specific alignments of constellations with planets and stars? $\endgroup$ Sep 22, 2017 at 13:42
  • $\begingroup$ If you are asking about planetary positions as well; there are plenty of magazines, programs like Celestia or RedShift, web sites. Might be best to add that to your post. $\endgroup$
    – user10106
    Sep 22, 2017 at 13:51
  • $\begingroup$ I'm very curious if there are any records from 2000 years ago of accurate predictions of current planet and star positions and if so; what is known of their methods? $\endgroup$ Sep 22, 2017 at 14:16
  • $\begingroup$ Stellarium (free program) has back-predictions that are accurate up to 2000 B.C. I've confirmed that myself by checking old Babylonian data of eclipses and stellar occultations around 500 BC. If you're asking the other direction, no 2000 years ago nobody could have predicted any planetary position. $\endgroup$ Sep 22, 2017 at 14:16

2 Answers 2


No, there is no possible way that humans from any known civilization in the first century AD would have been able to extrapolate current constellation positions.

Prior to the work of Johannes Kepler and Isaac Newton, humans did not have sufficient knowledge of the basic principles of celestial movement to have any kind of basis for making such calculations.

Second, even if they had the basic principles, they would also have needed much more accurate and detailed information about the makeup of the Milky Way galaxy. The information currently available, that goes into the NASA models, is the product of a great many man-years invested in both observations and analysis of those observations.

Third, even if they had the basic principles and the necessary details with which to create a proper model, they lacked the computing power necessary to actually run the model - computation of that time being limited to pencil and paper (or perhaps an abacus).

  • $\begingroup$ Would you feel that software models that "turn back the clock" are accurate? $\endgroup$ Oct 26, 2017 at 11:25
  • $\begingroup$ @DougKimzey It is as accurate as we can currently make it. Not being an actual astronomer, I don't know what the limitations of our current understanding are. $\endgroup$ Oct 26, 2017 at 15:34

What you're asking for in the comments, on ancient predictions, that's a tricky subject. You're basically talking about proper motion and Edmund Halley was the first person to observe it. He recognized that 3 stars were about 1/2 a degree from where they were observed 1,850 years earlier.


1/2 of 1 degree in the night sky is larger than you might think. It's about the diameter of the full moon, but 1,850 years is a long time. That's why it went unnoticed until Halley took a closer look at the ancient star charts.

It's noted in the Wikipedia article that the ancient Greeks suspected proper motion happened but they were unable to observe it and nobody can make a decent prediction based on something that changes so slowly they are unable to observe it.

With today's observation methods, it's just a matter of running a computer simulation to see what the constellations will look like 100 years from now (virtually unchanged) or 10,000 years from now (some of them would begin to be visibly skewed but likely still recognizable).

Every star has it's own proper motion, so each constellation would undergo it's own rate of change.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .