XMM-Newton Science Analysis System
eposcorr (eposcorr-3.13) [xmmsas_20190531_1155-18.0.0]
Some spherical geometry
eposcorr
calculates angular distances directly using spherical
trigonometry. In particular the following is used to calculate the angular
distance,
, between two sources (labeled 1 and 2).
![\begin{displaymath}
\cos( \theta) = \sin(\delta_1) \sin(\delta_2) + \cos(\delta_1) \cos(\delta_2) cos(\Delta\alpha),
\end{displaymath}](img25.png) |
(9) |
where
refers to the declination of a source and
, the difference of the right ascension of
the two sources.
XMM-Newton SOC/SSC -- 2019-06-02