archeo plugin: include limits of precession area

[axd1967]

Is your feature request related to a problem? Please describe. Some stars are not always visible from a given location, due to precession.

I'd like to see the entire sky area that might have been visible from a given location throughout the entire 26k yrs precession cycle.

Describe the solution you'd like Include a ArcheoLines setting "precession extrema" that draws 2 extrema that are visible from the current latitude:

• the highest declination (= sky area that is always visible throughout the cycle; the highest limit of the circumpolar circle across the cycle)
• lowest declination (=sky area that is visible halfway in the precession cycle; lowest limit of the circumpolar circle)

This creates a band of 2 x 23d56m wide that should be centered on the NEP and is probably centred on the ecliptic plane (to confirm).

These lines are complementary to the precession circles.

Describe alternatives you've considered

1. Time jumping works but does not provide a way to compare what areas become visible or not

Additional context Add any other context or screenshots about the feature request here.

ps - include an option to disable proper motion. this is for educational purposes, to simplify the presentation of the issue to specific audiences. Also, this proper motion is an approximation that might not reflect the actual (absolute or relative...) movement of stars over time

[gzotti]

Do you mean circumpolar at current location and over whole precession period? Can you work out the declination? It could speed up things. What is the short but comprehensive name for such lines? And the application within any culture?

[axd1967]

the antipodal circumpolar circle might be indirectly involved in this issue but is applicable for the selected date, and is centred on the NCP (which is the centre of the circumpolar circle), while we need circles centred on the NEP.