WINTER SOLSTICE: Everybody knows that December 21 is the shortest day of the year but not many people know why. The Sun reaches its maximum southern declination of the year. For those of us in the northern hemisphere, that means the noon Sun is lowest in the sky of any date of the year. From latitude 40 degrees north (New… Continue reading
In our newsletter and in our Signs & Seasons curriculum, we simply try to point out the easily-observable aspects of Classical Astronomy that are usually overlooked in our modern generation. One of those aspects is the varying length of shadows over the span of the year. As the Sun moves through the zodiac constellations over the annual cycle of the… Continue reading
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During May, the days grow long much less than in April, since the Sun increases only 7 degrees in declination, compared to 14-1/2 degrees in that previous month. (Compare with the previous month’s graphics.) The length of daylight only increases between 23 to 54 minutes for most locations in the USA, whereas daylight increased nearly two hours in April.… Continue reading
Due to the Earth’s annual revolution, the line of sight between the Sun and the background constellations is constantly changing. This appears as the Sun moving east through the constellations of the zodiac. During April, the Sun appears to be moving from the constellation Pisces into Aries. In the process, the Sun appears to be moving north from the celestial… Continue reading
During April, the days grow significantly longer since the equinox (the first day of spring). The Sun rises earlier and sets later, and is now quite high in the sky at noon. As a result, by month’s end, the length of daylight is almost two hours longer than at the beginning of spring. Note in the figure that, by… Continue reading
Twilight is the shortest during the spring and fall. In the morning, before sunrise, daylight comes on quickly closest to the equinoxes. In the evening, after sunset, night falls quickly, as the sky fades after sunset. Equinoctial twilights can be 45 minutes in the mid-temperate latitudes of North America. However, summer twilights are the longest of the year! In… Continue reading
SPRING BEGINS TODAY AT 6:45 PM EDT. This is the precise moment when the Sun is centered on the VERNAL EQUINOX. The vernal equinox is actually a location in the starry sky, the origin of the coordinate system of the celestial sphere. The place of the vernal equinox is where the celestial equator (0 degrees of declination) intersects with… Continue reading
On the vernal equinox, the Sun rises perfectly due east, and sets 12 hours later, exactly due west. Be sure to notice this if you can see the sunrise or sunset on the day of the equinox, March 20. The Sun is on the celestial equator, the midpoint between the celestial poles, balanced between the northern and southern constellations.… Continue reading
