Return the equivalency to convert between a physical distance on the Sun and an angular separation as seen by a specified observer.
This equivalency assumes that the physical distance is perpendicular to the Sun-observer line. That is, the tangent of the angular separation is equal to the ratio of the physical distance to the Sun-observer distance. For large physical distances, a different assumption may be more appropriate.
SkyCoord) – Observer location for which the equivalency is calculated.
equiv (equivalency function that can be used as keyword
equivalenciesfor astropy unit conversion.)
>>> import astropy.units as u >>> from sunpy.coordinates import get_body_heliographic_stonyhurst >>> earth_observer = get_body_heliographic_stonyhurst("earth", "2013-10-28") >>> distance_in_km = 725*u.km >>> distance_in_km.to(u.arcsec, equivalencies=solar_angle_equivalency(earth_observer)) INFO: Apparent body location accounts for 495.82 seconds of light travel time [sunpy.coordinates.ephemeris] <Quantity 1.00603718 arcsec>