Parallactic angle¶
- PyAstronomy.pyasl.parallacticAngle(t, gl, dec)¶
Calculate the parallactic angle
The parallactic angle is the position angle of the zenith at the target.
- Parameters
- tfloat or array
Hour angle [deg]
- glfloat
Latitude of the observer [deg]
- decfloat
Declination of the target [deg]
- Returns
- qfloat or array
The parallactic angle [deg]
Notes
Useful links
Example: Parallactic angle for objects observed by Keck¶
import numpy as np
import matplotlib.pylab as plt
from PyAstronomy import pyasl
# Geo-latitude of Keck [deg]
gl = 19.83
# Declinations to be considered
decs = np.arange(-80, 81, 20)
# Hour angles to be considered
t = np.linspace(0.0, 8*15, 1000)
for dec in decs:
q = pyasl.parallacticAngle(t, gl, dec)
plt.plot(t/15, q, '-', label="$\delta = $" + f"{dec} deg")
plt.ylabel("Parallactic angle [deg]")
plt.xlabel("Hour angle [h]")
plt.legend()
plt.show()
