本帖最後由 WCYue 於 2023-6-20 12:32 編輯
以下是使用上述提到的部分庫進行月掩星和小行星掩星預測的示例代碼:
1. 使用 Skyfield 預測月掩星
```python
from skyfield.api import Topos, load
from skyfield.almanac import find_discrete
from skyfield import almanac_east_asia
ts = load.timescale()
t0 = ts.utc(2023, 1, 1)
t1 = ts.utc(2023, 12, 31)
eph = load('de440.bsp')
earth = eph['earth']
moon = eph['moon']
sun = eph['sun']
observer = earth + Topos('35.6895 N', '139.6917 E') # Example: Tokyo(日本東京)
def occultation(t):
astrometric = observer.at(t).observe(sun)
apparent = astrometric.apparent()
separation = apparent.separation_from(observer.at(t).observe(moon).apparent())
return separation.degrees
t_occultation, is_occulted = find_discrete(t0, t1, occultation)
for t, occulted in zip(t_occultation, is_occulted):
if occulted:
print(f"Lunar occultation begins at {t.utc_strftime('%Y-%m-%d %H:%M:%S')} UTC")
else:
print(f"Lunar occultation ends at {t.utc_strftime('%Y-%m-%d %H:%M:%S')} UTC")
```
2. 使用 Astropy 預測小行星掩星(以小行星 Ceres 為例)
```python
import numpy as np
from astropy.time import Time
from astropy.coordinates import SkyCoord, EarthLocation, AltAz
from astroquery.jplhorizons import Horizons
# Set observing location and time range
location = EarthLocation(lat=35.6895, lon=139.6917) # Example: Tokyo
time_start = Time("2023-01-01", format='iso', scale='utc')
time_end = Time("2023-12-31", format='iso', scale='utc')
time_interval = 60 # minutes
time_range = Time(np.arange(time_start.jd, time_end.jd, time_interval / 1440), format='jd', scale='utc')
# Query Ceres ephemeris
ceres = Horizons(id='1', location=location, epochs=time_range.jd, id_type='id')
ceres_ephem = ceres.ephemerides()
# Query star positions (using a star catalog, e.g. Gaia; here we use a fake star for demonstration)
star_ra = 180.0 # Example: RA in degrees
star_dec = 0.0 # Example: Dec in degrees
star_coord = SkyCoord(ra=star_ra, dec=star_dec, unit='deg', frame='icrs')
# Check if Ceres occults the star
ceres_coord = SkyCoord(ra=ceres_ephem['RA'], dec=ceres_ephem['DEC'], unit='deg', frame='icrs')
separation = ceres_coord.separation(star_coord).arcsecond
occultation_threshold = 0.5 # arcseconds, assuming Ceres angular size
occultation_indices = np.where(separation < occultation_threshold)[0]
for idx in occultation_indices:
occultation_time = time_range[idx]
print(f"Asteroid occultation (Ceres) occurs at {occultation_time.utc_strftime('%Y-%m-%d %H:%M:%S')} UTC")
```
請注意,這些代碼示例可能需要安裝相應的 Python 库和數據文件。此外,為了獲得準確的預測結果,可能需要調整觀測地點、時間範圍等參數。在使用這些代碼時,請根據實際需求進行相應的修改。 |