Problems And Solutions — Spherical Astronomy

A star's coordinates are given for the J2000 epoch. Why are these coordinates "wrong" for an observation taken today?

δ>90∘−ϕdelta is greater than 90 raised to the composed with power minus phi spherical astronomy problems and solutions

cosa=cosbcosc+sinbsinccosAcosine a equals cosine b cosine c plus sine b sine c cosine cap A A star's coordinates are given for the J2000 epoch

Will a star with a declination of +60° ever set for an observer at latitude 45°N? spherical astronomy problems and solutions