sunpy.coordinates.ephemeris.get_sun_L0(time='now') [edit on github]

Deprecated since version 1.0: This is scheduled for removal in 2.1.

Return the L0 angle for the Sun at a specified time, which is the Carrington longitude of the Sun-disk center as seen from Earth.


time (tuple, str, pandas.Timestamp, pandas.Series, pandas.DatetimeIndex, datetime.datetime,, numpy.datetime64, numpy.ndarray, astropy.time.Time) – Time to use in a parse_time-compatible format


Longitude – The Carrington longitude


This longitude is calculated using current IAU values (Seidelmann et al. 2007 and later), which exclude the effects of light travel time and aberration due to Earth’s motion (see that paper’s Appendix). This function then applies the effects of light travel time and aberration, which is the approach of the Astronomial Almanac. Applying the aberration due to Earth’s motion (~20.5 arcseconds) is required because the IAU values were tuned under the assumption that it would be done (see Urban & Kaplan 2007).


  • Seidelmann et al. (2007), “Report of the IAU/IAG Working Group on cartographic coordinates and rotational elements: 2006” (link)

  • Urban & Kaplan (2007), “Investigation of Change in the Computational Technique of the Sun’s Physical Ephemeris in The Astronomical Alamanac” (link)