solar_angle_equivalency

sunpy.coordinates.utils.solar_angle_equivalency(observer)[source]

Return the equivalency to convert between a physical distance on the Sun and an angular separation as seen by a specified observer.

Note

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.

Parameters:

observer (SkyCoord) – Observer location for which the equivalency is calculated.

Returns:

equiv (equivalency function that can be used as keyword equivalencies for astropy unit conversion.)

Examples

>>> 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>