Question

Listed following are the declinations of five different stars. Rank these declinations from left to right based on the maximum altitude (on the meridian) each star reaches for an observer at latitude 60°N, from lowest altitude (nearest the horizon) to highest altitude (farthest above the horizon).

The diagram shows a person standing on the Earth's surface looking up at the sky in the direction or altitude indicated.

Answer 1

For latitude 60°N, the celestial equator extends from due east on the horizon to due west on the horizon, crossing the meridian at an altitude of 90°- 60° = 30° (in the south). Because the start with the dec = +30° lies 30° to the north of the celestial equator on the celestial sphere, it must cross the meridian at a point 30° to the north of where the celestial equator crosses, which means at an altitude of 60°. The same reasoning explains the rest of the rankings, for example, the star with dec = -20° lies 20° to the south of the celestial equator on the celestial sphere, so it must cross the meridian at a point 20° to the south of where the celestial equator crosses, which means it’s at an altitude of 10°.

Therefore, the answers are as follows:

Nearest the Horizon
dec = -20 degrees
dec = -5 degrees
dec = +0 degrees
dec = +10 degrees
dec = +30 degrees
Farthest Above the Horizon