Why switch to another standard equinox and epoch?
Calculations of the visibility of celestial objects for an observer at a specific location on Earth require the equatorial coordinates of the objects, relative to the equinox of the date. If the coordinates relative to some other equinox are used, then that will cause errors in the results. The magnitude of those errors increases as the time difference compared to the equinox of the date increases, because of precession of the equinoxes. If the time difference is small, then fairly easy and small corrections for the precession suffice. If the time difference gets large, then tedious, complicated corrections must be applied. So, a stellar position read from a star atlas or catalog that is based on a sufficiently old equinox cannot be used without tedious corrections, at least not if reasonable accuracy is required. Additionally, star positions change even if the coordinate system does not, because the stars move relative to each other through space. The apparent motion along the sky rel
