If enough time variation is compact, then relatively straightforward and small corrections with the precession may suffice. If some time difference receives big, then fuller and even more correct corrections have to be applied. This is why, a star posture study from a star atlas or catalog depending on a adequately outdated equinox and equator can

If enough time big difference is small, then rather quick and tiny corrections for that precession might suffice. If time variance will get large, then fuller and more precise corrections need to be utilized. This is why, a star place examine from a star atlas or catalog depending on a adequately previous equinox and equator can not be employed wit