Thuban (α Draconis) – closest approach to North Celestial Pole (Stellarium vs. other sources)

[electroreceptive1970]

Hello,

I am comparing Stellarium results with various archaeoastronomical and educational sources regarding the epoch when Thuban (α Draconis) was closest to the North Celestial Pole.

Stellarium shows the minimum separation of about 0.16°, around 2780 BCE.

Other sources report slightly different epochs and distances:

Giulio Magli (2009), Architecture, Astronomy and Sacred Landscape in Ancient Egypt

Juan Antonio Belmonte (2009), In Search of Cosmic Order

Clive Ruggles, Handbook of Archaeoastronomy

EarthSky: ~2787 BCE almost exactly on the pole; another EarthSky article gives 2830 BCE with ~10 arcminutes (≈0.17°) separation

Encyclopaedia Britannica: closest to the pole around 2700 BCE

Wikipedia (Thuban): closest in 2830 BCE, <10 arcminutes from the pole

Wikipedia (Pole star): in 3000 BC, Thuban aligned within 0.1° of the pole – the closest of any visible pole star

My questions:

Which precession model and algorithms does Stellarium use for stellar positions at such remote epochs?

How is proper motion of Thuban implemented?

Could these factors explain the differences in both epoch (2830–2700 BCE) and angular distance (0.1°–0.3° vs Stellarium’s 0.16°)?

I would like to know how reliable Stellarium’s output is for archaeoastronomical research at this level of precision.

Thank you!

[gzotti]

I see min distance in -2800. Make sure your are running 25.2 or later.

• Appendix F.5 and F.2
• Appendix F.2
• Most probably. Ask Magli, JAB, Clive, EarthSky, EB, Wikipedia for their sources.
• All of these and our computations aim to "find the right solution", based on whatever models are available. Some secondary sources probably copy copies from copies from earlier years. We did not measure ourselves. You could probably compare all these data in your paper, and provide a tree of consequences (changed chronological sequences?).