Epoch vs . equinoxDate-references for coordinate systemsEpochs and durations of validityChanging the regular equinox and epochSpecifying an epoch or equinoxBesselian yearsJulian several years and J2000Epoch of your daySee alsoReferencesNotesCitationsSourcesFurther readingExternal backlinksThe primary usage of astronomical portions laid out in this

An illustration of how this is effective: if a star's position is measured by anyone nowadays, they then use a regular transformation to obtain the position expressed when it comes to the normal reference frame of J2000, and it is commonly then this J2000 situation and that is shared with others.So, some stellar positions browse from the star atlas