The Seasonal Almanac: Events for April and May 1996

The Seasonal Almanac covers astronomical events and nature, including Venus, a lunar eclipse, azaleas and rhododendrons and when Easter occurs.

Rhododendron seasonal almanac

The most fascinating feature of rhododendrons is the temperature behavior of their leaves, which enables us to use them as natural thermometers. The greater the angle of uplift in the rhododendron leaves, the higher the temperature.


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The Seasonal Almanac shares astronomical events in April and May 1996. Brilliant Venus will actually cast shadows in May. 

The Seasonal Almanac: Events for May 1996

Venus is the brightest point of light in the heavens. But this spectacular planet is fairly close to the Sun in space and therefore always appears fairly close to the Sun in our sky. We are lucky when Venus is visible for more than an hour or two before sunrise or more than an hour or two after sunset. And this spring we are luckiest of all: in its eight-year cycle of recurring appearances, this is the spring that Venus soars to its highest in the evening sky. As April begins, the brilliant "evening star" hangs halfway up the southwest sky at sunset and does not itself sink below the horizon until about four hours later.

A bonus for Venus watchers occurs at the start of April. On April 2 and 3, Venus is skimming right along the edge of the loveliest of all star clusters, the Pleiades, or "Seven Sisters," cluster. Although the cluster is usually easy to see with the naked eye, the brilliance of Venus may so overwhelm its stars that we'll need binoculars to spot them plainly. The next few nights, no optical aid should be required to view the wonderful little grouping of sapphire-like stars being left behind by the peerless diamond of Venus.

Venus is noticeably lower at sunset by early May, but to make up for this, the planet gets even brighter. The maximum brilliance of Venus is almost unbelievable, especially as seen from a rural site, where Venus is even capable of casting shadows in a very dark location. Try to see how soon before sunset each day you can first glimpse Venus. On days of deep-blue sky, the planet can even be found in the middle of the day with the unaided eye!

The final weeks of May bring us the drama of Venus appearing appreciably lower with each passing night. At the start of May, Venus sets over three and a half hours after the Sun, but by the end of the month, only about one hour after. And if you have a small telescope or even a pair of binoculars you can hold steady, there is another wonder of Venus to behold: the changing phase of the planet. Venus is a planet closer to the Sun than Earth is, and it displays to us phases like the moon does (fully lit globe of Venus, half-Venus, crescent Venus ... ) Of course, normally you need a fairly good telescope to detect these phases. But in May, Venus is approaching unusually close to Earth (not dangerously close, don't worry!). So even binoculars may show it as more of a long, skinny crescent than as the simple point of light it looks like to the naked eye.

A Total Lunar Eclipse for the Eastern U.S.  

Not since 1993 has the Earth experienced a total eclipse of the Moon. On April 3, 1996, however, the Moon rises just in time for the northeastern United States to see the start of the total part of such an eclipse. In the southeastern United States and across the Midwest, the Moon comes up with the Earth's "umbra," or central shadow, already completely covering the Moon. From the Rockies, viewers see the umbra already moving off the Moon, and Pacific Coast observers are left with only the slight stain of Earth's outer shadow, the "penumbra," on the Moon when it rises.

The rising Moon often looks dimmer and more orange due to haze down near the horizon. But as people in the eastern half of the country see this Full Moon of Wednesday April 3, get higher, they will know that the Moon is more unusually darkened and colored. No one can predict exactly how dark the Earth's shadow is in the different parts the Moon goes through during an eclipse, or what colors are in various parts of that shadow. But this eclipse will prob ably be a moderately dark one, especially near the Moon's northern edge around mid-eclipse—7:10 P.M. EST. The sky won't be fully dark by then even in New England. But the total portion of the eclipse doesn't end until 7:53 P.M. EST, and the last bit of umbra slides off the Moon at 8:59 P.M. EST.

Fortunately, all of the United States will be suitably positioned to see the entire total eclipse of the Moon we will get on the evening of September 26, 1996. That eclipse occurs at Harvest Moon and the planet Saturn will shine beautifully at its brightest very near the dimmed and reddened lunar disk.

Azaleas and Rhododendrons  

While lunar eclipses bring added color to the night sky, we don't have to look far to find hues of all kinds in the birds and the flowers of April and May. Even regions whose soil does not support many kinds of plant life still may support a few unusual plants. For instance, if your soil is naturally very acidic, perhaps because you live in or near pine forests, then you should have little trouble growing the fascinating flowering plants called azaleas and rhododendrons.

The yellow blossomed forsythia also likes acidic soil, and if you live in the northern United States you may see their blooms linger through much of April. But May is the greatest month of flowers in most of the United States and it is then that many of the azaleas and rhododendrons reach their peak.

The flowers on azalea bushes are trumpet-shaped and as such a favorite feeding-place of hummingbirds. (Watch your May-blooming azaleas for ruby-throated hummingbirds hovering and inserting their long tubelike beaks into the flowers for nectar to help sustain them on their northward migration.) The most common azalea colors are pink, purple, and white, but further breeding has produced red, gold, and orange. The blossom sizes range from small thimbles to palm-filling bells.

The rhododendron is perhaps even more interesting, if no more beautiful, than azaleas. Some "rhodies" blossom in summer. Their most common colors are white and purple, though again special breeding has produced other lovely hues. The rhododendrons are clearly related to the wild-growing mountain laurel, itself beautiful enough to be honored as a state flower. But the most fascinating feature of rhododendrons is the temperature behavior of their leaves, which enables us to use them as natural thermometers. The greater the angle of uplift in the rhododendron leaves, the higher the temperature.

The leaves stay on the plant all year and it is quite remarkable on the coldest winter days to see their long forms closed up (looking almost like bean pods) and pointing straight down. In winter, when you wake up in a warm house, you can glance at the rhododendrons and estimate whether the air outside is 30 degrees Fahrenheit or 10 degrees Fahrenheit. In May and June, the lovely widespread flower clusters may distract, but you can still notice just how chilly the dawn is or see if the day is one of those throwbacks to early spring which still creep in even when summer is at the doorstep.

When Do We Hold Easter?  

For the past 10 years, most Americans have made the clock change from Standard to Daylight Saving Time on the first Sunday in April—which this year happens to be Easter.

But what is the rule for when Easter occurs? Ideally, the system for determining the date of Easter is as follows. Take the date of the spring equinox (the start of spring). Then find the first full moon either on or after that date. Easter is the first Sunday after the day of that full moon. (Easter can never occur on the day of a full moon.)

However, there can be departures from this ideal system. For instance, church authorities decided to accept the date of spring equinox as March 21. But, as astronomers tell us, the equinox can actually fall on March 19, 20, or 21 in our era of history, depending upon slight variations of Earth in its orbit and upon leap years (for instance, this year having a leap day at the end of February made the spring equinox fall in the opening hours of March 20 for the continental United States, and not on March 21 anywhere.).

In practice, therefore, the date of Easter is actually determined by special formulas, such as the table of Golden Numbers in the prayer book. When all is said and done, the earliest that Easter can occur is March 22 (if the full moon occurs on March 21 and March 21 is a Saturday) and the latest Easter can occur is April 25 (if the full moon is on March 20 and April 18 is a Sunday).

The last time Easter occurred on March 22 was in 1818; the next time will not be until 2285! In the year 2009, Easter will take place as early as March 23 for the first time since 1913. The last time Easter occurred on April 25 was 1943, and the next time will be in 2038.