Does the declination of a distant star change with the seasons or is it constant ?

Question

if it is constant how is angle above the horizon of a star calculated

Answer 1

Declination is the equivalent of latitude, and is part the position in the sky of a star as measured at the vernal equinox.

Since the equinoxes precess, in fact declination does change vary slightly with time. if the star is distant, proper motion won't make any difference, but closer stars move.

Try looking at Simbad:

http://simbad.u-strasbg.fr/simbad/sim-fi...

put in the name of a star (say Betelgeuse)

It will give you the coordinates for years 1950 and 2000

yr 2000               05 55 10.305 +07 24 25.43

yr 1950               05 52 27.80 +07 23 57.8  

the declination has changed by less than an arcminute in 50 years - but it has changed.

Answer 2

The declination of a star remains the same throughout the year. However, that declination as seen from Earth will change due to the seasons. The angle of a star above the horizon is different from its declination and is nothing more than the current angular position in degrees above the local horizon.