histastro.coordinates module

Coordinate transformations and related functions for HistAstro.

histastro.coordinates.ecl2eq(lon, lat, eps)[source]

Convert (geocentric) spherical ecliptical coordinates to spherical equatorial coordinates.

Parameters:
  • lon (float) – Ecliptical longitude (rad).

  • lat (float) – Ecliptical latitude (rad).

  • eps (float) – Obliquity of the ecliptic (rad).

Returns:

tuple containing (ra, dec):

  • ra (float): Right ascension (rad).

  • dec (float): Declination (rad).

Return type:

tuple (float,float)

References

histastro.coordinates.eq2ecl(ra, dec, eps)[source]

Convert equatorial coordinates to ecliptical.

Parameters:
  • ra (float) – Right ascension (rad).

  • dec (float) – Declination (rad).

  • eps (float) – Obliquity of the ecliptic (rad).

Returns:

tuple containing (lon, lat):

  • lon (float): Ecliptical longitude (rad).

  • lat (float): Ecliptical latitude (rad).

Return type:

tuple (float,float)

histastro.coordinates.geoc2topoc_ecl(gcLon, gcLat, gcDist, gcRad, eps, lst, obsLat, obsEle=0, debug=False)[source]

Convert spherical ecliptical coordinates from the geocentric to the topocentric system.

Parameters:
  • gcLon (float) – Geocentric ecliptic longitude (rad).

  • gcLat (float) – Geocentric ecliptic latitude (rad).

  • gcDist (float) – Geocentric distance (AU).

  • gcRad (float) – Geocentric semi-diameter (rad).

  • eps (float) – Obliquity of the ecliptic (rad).

  • lst (float) – Local sidereal time (rad).

  • obsLat (float) – Geographical latitude of the observer (rad).

  • obsEle (float) – Altitude/elevation of the observer above sea level (metres, optional, default value = 0).

  • debug (float) – Print debug output (True/False, optional, default value = True).

Returns:

tuple containing (tcLon, tcLat, tcRad):

  • tcLon (float): Topocentric ecliptic longitude (rad).

  • tcLat (float): Topocentric ecliptic latitude (rad).

  • tcRad (float): Topocentric semi-diameter (rad).

Return type:

tuple (float,float,float)

histastro.coordinates.obliquity(jd)[source]

Compute the obliquity of the ecliptic in radians from the JD(E).

Parameters:

jd (float) – Julian day (days).

Returns:

eps: Obliquity of the ecliptic (rad).

Return type:

float

References

  • Seidelman 1992, Eq. 3.222-1.

histastro.coordinates.par2horiz(ha, dec, phi)[source]

Convert parallactic coordinates to horizontal.

Parameters:
  • ha (float) – Hour angle (rad).

  • dec (float) – Declination (rad).

  • phi (float) – Geographical latitude (rad, N>0).

Returns:

tuple containing (az, alt):

  • az (float): Azimuth (rad, S=0).

  • alt (float): Altitude (rad).

Return type:

tuple (float,float)

histastro.coordinates.precessHip(jd, ra, dec)[source]

Compute precession in equatorial coordinates from the Hipparcos equinox (J2000) to that of the specified JD.

Parameters:
  • jd (float) – Julian day (days).

  • ra (float) – Right ascension (rad).

  • dec (float) – Declination (rad).

Returns:

tuple containing (raTarget, decTarget):

  • raNew (float): Right ascension for the target equinox (rad).

  • decNew (float): Declination for the target equinox (rad).

Return type:

tuple (float,float)

histastro.coordinates.properMotion(startJD, targetJD, ra, dec, pma, pmd)[source]

Compute the proper motion from startJD to targetJD for the given positions and proper motions.

Parameters:
  • startJD (float) – Julian day of the initial epoch (days).

  • targetJD (float) – Julian day of the target epoch (days).

  • ra (float) – Right ascension (numpy array, rad).

  • dec (float) – Declination (numpy array, rad).

  • pma (float) – Proper motion in right ascension (numpy array, rad/yr).

  • pmd (float) – Proper motion in declination (numpy array, rad/yr).

Returns:

tuple containing (raTarget, decTarget):

  • raTarget (float): Right ascension for the target epoch (rad).

  • decTarget (float): Declination for the target epoch (rad).

Return type:

tuple (float,float)