**XMM-Newton Science Analysis System
**

eposcorr (eposcorr-3.13) [xmmsas_20211130_0941-20.0.0]

##

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).
(9)
where refers to the declination of a source and
, the difference of the right ascension of
the two sources.

XMM-Newton SOC -- 2021-11-30