tpxes¶
-
erfa.
tpxes
(a, b, a0, b0)[source]¶ Wrapper for ERFA function
eraTpxes
.- Parameters
a : double array
b : double array
a0 : double array
b0 : double array
- Returns
xi : double array
eta : double array
Notes
The ERFA documentation is below.
- - - - - - - - - e r a T p x e s - - - - - - - - - In the tangent plane projection, given celestial spherical coordinates for a star and the tangent point, solve for the star's rectangular coordinates in the tangent plane. Given: a,b double star's spherical coordinates a0,b0 double tangent point's spherical coordinates Returned: *xi,*eta double rectangular coordinates of star image (Note 2) Returned (function value): int status: 0 = OK 1 = star too far from axis 2 = antistar on tangent plane 3 = antistar too far from axis Notes: 1) The tangent plane projection is also called the "gnomonic projection" and the "central projection". 2) The eta axis points due north in the adopted coordinate system. If the spherical coordinates are observed (RA,Dec), the tangent plane coordinates (xi,eta) are conventionally called the "standard coordinates". For right-handed spherical coordinates, (xi,eta) are also right-handed. The units of (xi,eta) are, effectively, radians at the tangent point. 3) All angular arguments are in radians. 4) This function is a member of the following set: spherical vector solve for > eraTpxes < eraTpxev xi,eta eraTpsts eraTpstv star eraTpors eraTporv origin References: Calabretta M.R. & Greisen, E.W., 2002, "Representations of celestial coordinates in FITS", Astron.Astrophys. 395, 1077 Green, R.M., "Spherical Astronomy", Cambridge University Press, 1987, Chapter 13. Copyright (C) 2013-2019, NumFOCUS Foundation. Derived, with permission, from the SOFA library. See notes at end of file.