Re: The 3 minute 56 second illusion

Odysseus wrote:
In article <ri5Ul.1677$9L2.596@xxxxxxxxxxxxxxxxxxxx>,
skyguy <skyguy@xxxxxxxxxxx> wrote:

<snip>

It can be difficult to understand how the rising point (azimuth) of the sun on the equator does shift during the year but it always rises perpendicularly. It seems more intuitive to visualize the sun always rising due east on the equator, but taking a different track, depending on the time of year. The actual case is hard to imagine because it involves visualizing the curved path of the sun across the sky as seen by an observer on an apparently flat earth.


Or using an old-fashioned horizon diagram, which will make it clear that the azimuth of the Sun's rising always depends on its declination. For an observer on the Equator the diagram shows the celestial equator as a straight east-west line that divides the horizon circle in half, meeting the prime vertical at the zenith; on any day other than an equinox the Sun keeps to one side or the other throughout its arc, according to its N or S declination.


Of course the stars and all other celestial objects take similar paths as seen from the equator depending on their declination but we don't seem no notice that as much as we do for the sun. The effect is best illustrated in a planetarium where you can see how the sun always rises vertically at the equator although it rises due east on only two days of the year (equinoxes). We are nearing the time now when the sun will be rising at the equator at it's farthest point to the north (left) of east but it still rises vertically. The path curves towards the north until it reaches the highest point in the sky at local noon where the sun will be 23.5-deg to the north of the zenith.
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