Editing Radial velocity (section)

===Data reduction===
From the instrumental perspective, velocities are measured relative to the telescope's motion. So an important first step of the [[data reduction]] is to remove the contributions of
*the [[Earth's orbit|Earth's elliptic motion]] around the Sun at approximately ± 30&nbsp;km/s,
*a [[Orbit of the Moon|monthly rotation]] of ± 13&nbsp;m/s of the Earth around the center of gravity of the Earth-Moon system,<ref name="FMelloLNP683">{{cite book|first1=S. |last1=Ferraz-Mello |first2=T. A. | last2=Michtchenko |title=Chaos and Stability in Planetary Systems |chapter=Extrasolar Planetary Systems |pages=219–271|series=Lecture Notes in Physics | volume=683| year=2005| doi=10.1007/10978337_4| bibcode=2005LNP...683..219F|isbn=978-3-540-28208-2 }}</ref>
*the [[Earth's rotation|daily rotation]] of the telescope with the Earth crust around the Earth axis, which is up to ±460&nbsp;m/s at the equator and proportional to the cosine of the telescope's geographic latitude,
*small contributions from the Earth [[polar motion]] at the level of mm/s,
*contributions of 230&nbsp;km/s from the motion around the [[Galactic Center]] and associated proper motions.<ref name="Reiadarxiv1608">{{cite journal|arxiv=1608.03886|first1= M. J. |last1=Reid|first2=T. M. |last2=Dame|title=On the rotation speed of the Milky Way determined from HI emission|year=2016|doi=10.3847/0004-637X/832/2/159|volume=832|issue= 2 |journal=The Astrophysical Journal|page=159|bibcode = 2016ApJ...832..159R |s2cid= 119219962 |doi-access= free }}</ref>
*in the case of spectroscopic measurements corrections of the order of ±20&nbsp;cm/s with respect to [[Relativistic aberration|aberration]].<ref name="StumpffAA">{{cite journal|first1=P. |last1=Stumpff|year=1985|journal=Astron. Astrophys. |bibcode=1985A&A...144..232S |title=Rigorous treatment of the heliocentric motion of stars |volume=144 |issue=1| pages=232}}</ref>
*[[Sin i degeneracy]] is the impact caused by not being in the plane of the motion.