Plotting for much earlier times

[paweel-srt]

I can't get what i'm doing wrong or there is some bug. When i'm trying to plot Orthographic Map for let's say begining of common era (using de441 ephemeris) the vernal equinox is stil at it current position. Nothing changes.

from datetime import datetime
from zoneinfo import ZoneInfo

from starplot import MapPlot, Orthographic, Observer, _
from starplot.styles import PlotStyle, extensions


style = PlotStyle().extend(
    extensions.BLUE_GOLD,
    extensions.MAP,
)

tz = ZoneInfo("Asia/Kolkata")
dt = datetime(200, 1, 19, 21, 00, tzinfo=tz)

observer = Observer(
    dt=dt,
    lat=23.17,
    lon=75.79,
)
p = MapPlot(
    projection=Orthographic(
        center_ra=observer.lst,
        center_dec=observer.lat,
    ),
    observer=observer,
    ephemeris = 'de441.bsp',
    style=style,
    resolution=10000,
    scale=1
)
p.gridlines(labels=False)
p.constellations()
p.constellation_borders()

p.stars(where=[_.magnitude < 4], where_labels=[False])

p.ecliptic()
p.celestial_equator()
p.milky_way()

p.export("map_orthographic.png", padding=0.3, transparent=True)

[paweel-srt]

It seems like that there is no consideration of precession in calculations yet

[steveberardi]

Plotted stars should be plotted in their positions as described here, but the ecliptic (or rather, the angle between the celestial equator and ecliptic) is currently a static line (at a 23.4 degree angle from the CE). I didn't realize that angle changes over time, but makes sense! It would be fairly easy to make this line calculated from the observer's time, just a change to the ecliptic function. I'll put this on the roadmap, if you wanna try implementing it yourself, feel free -- I'd welcome a PR for it! :)