Wednesday, June 28, 2017

2017 Eclipse Corner #4 Types of Eclipses

     An eclipse is a blocking of light when one heavenly body moves into the shadow  of another heavenly body. Both the Sun and the Moon get caught in shadows and disappear from view of the earth. A lunar or Moon eclipse occurs in the full moon phase when the Moon is at the nodes or in alignment with the earth-sun plane. The shadow of the earth crosses the Moon creating 3 types of eclipses. The umbra portion of the earth’s shadow is where the direct shadow of the sunlight is blocked. This umbra will produce a total lunar eclipse if the whole moon is in the umbra. If only part of the Moon is in the umbra shadow then it will be a partial lunar eclipse. The penumbra shadow is not the direct shadow and only some of the light is blocked. Much of the time the penumbral eclipse is not noticeable.

     A penumbral eclipse is only of academic interest. It is very subtle and hard to observe.

     The Moon went through a penumbral lunar eclipse on February 11.  A lunar eclipse is reflected light from the Sun and presents no danger to the eyes. Because the Earth is much larger than the Moon, the totality portion of a lunar eclipse may block the Moon’s light for more than an hour. The number of lunar eclipses can vary from two to five per year. Because penumbral eclipses are so inconspicuous, most viewers are keeping track of only the umbral eclipses. Those are the partial and total lunar ones which can range from zero to three a year.
     Solar eclipses occur when the moon is in New Moon phase or between the Earth and the Sun. The Moon has to be in the line of the nodes or in alignment with the Sun-Earth plane. Often the alignment will place both the Solar and Lunar eclipse two weeks from each other.  This summer, a partial lunar eclipse is due for much of the world on August  7, but the central US will not see it. Two weeks later on August 21, 2017 will be our Total Solar Eclipse.

     Please observe the small portion of the earth receiving the umbral shadow. The total solar eclipse only covers a 170 mile width band as it moves across the earth. You must be in the right location.

There are three types of Solar eclipses.  A Partial solar eclipse is when we see only part of the Sun blocked out.  A Total Solar Eclipse is when the whole Sun is covered like what we will see in August. The third type is called an Annular Eclipse happens when the Moon is at apogee according to Kepler’s Laws and with a smaller shadow and fits inside the totality of the Sun and cannot produce totality.

     This picture shows Dan Slais as a National Park Ranger in Petrified Forest National Park showing the 2012 partial Eclipse. The method used here is an indirect view through a reflecting telescope on to a poster board.
Next time, Eclipse Corner will look at some Archeoastronomy and solar eclipses.   –Dan Slais

Join us August 18-21, 2017 for Midnight at Noon - a 4-day Music Festival and Eclipse Viewing Event.  For more information visit our website

Wednesday, June 21, 2017

2017 Eclipse Corner #3 Kepler's Law 1

     Several civilizations of the past kept records to allow accurate understanding of the night time sky. Europe had to get out of the Dark Ages using mathematics to describe natural phenomena. After Copernicus placed the planets in order around the Sun, science found both the Sun and the Moon vary in their distances from the Earth during different positions in their orbits. Based on Kepler’s First Law of Planetary Motion, the orbit of each planet around the Sun is the shape of an ellipse. An ellipse is an oval shaped conic section from which geometric exact calculations can be made of the objects position (where the sum of the distances from the two foci to every point on the loop is constant). The elliptical orbit of the Earth around the Sun has a minimal distance or closest point called perihelion and a maximum distance or farthest point called aphelion*. Perihelion was reached on January 4 this year and the aphelion will be reached in 2017 on July 3. 
*Information from Comins, Discovering the Essential Universe    

     The distance of difference between the aphelion and perihelion is more than three million miles. That seems like a lot of miles until one understands that the average distance to the Sun is 93 million miles and the difference is only 3%. Living in the northern hemisphere means we are closer to the Sun in winter and farther away in the summer. Of course the tilt of the earth causes the seasons, and we are tilted away in winter and towards the Sun in the summer. Although there are a variety of factors that affect the earth’s temperature, the aphelion and perihelion may give us cooler summers and warmer winters?        

     The mathematics of an ellipse shows the distance Focus 1 to the planet + Focus 2 to the planet = the same sum at any planet position on the elliptical orbit. Please notice aphelion is farther than perihelion.

      The revolution of the Moon also follows Kepler’s First Law being an ellipse. Because the Moon is closer to the Earth, the distances of the close and farther parameters are more noticeable. The orbit of the Moon occurs once a month so the closest point or perigee and farthest point or apogee occurs once a month. News media have recently used a new term “Supermoon” when the Full Moon Phase is at the perigee or closest point to the Earth and the Moon appeared much larger.
Sometimes during a Solar Eclipse, the Moon can be close to apogee, the Moon’s farthest point from the Earth, where it could be small enough to fit inside the Sun or produce what is called an Annular Eclipse. According to, our 2017 Solar Eclipse, August 21, the Moon is only 3 days from perigee, its closest point. From, mid-Missouri will have a Total Solar Eclipse and we will get over 2 minutes and 30 seconds of totality at the center line.                –Dan Slais

     Full moons at apogee(left) and perigee(right) in 2011.

Earthsky.corg/astronom-essentials Composite image by EarthSky community member C.B. Devgun in India

Monday, June 12, 2017

2017 Eclipse Corner #2 The Moon Orbit

The Moon is our most obvious viewable space neighbor and its daily changing phases are remarkable. The Moon produces no light, it simply reflects light from the Sun. Ancient farmers knew the best time to plant different crops and the best time harvest options based on the Moon. Today, the Farmer’s Almanac is still available for those farming facts. As the Moon orbits the earth, its path moves from west to east, changing position among the background stars.. It takes the Moon 29 ½ days to complete a revolution around the earth. That is how the calendar month was developed.
Lunar Phases

http://spaceplace.nasa. gov/review/dr-marc-earth/moon-phases.html

The Sun illuminates half the Moon at all times, but the earth’s position to the plane of the Sun-Moon allows us to see different “phases.” Following the picture, when the Moon is in line with the Sun the illuminated side of the Moon is opposite the earth. We do not see the Moon. This phase is called the New Moon. As the Moon moves in its revolution each day we see the phase getting larger or showing more light.  This is called waxing. After the Full Moon, the phases get smaller or show less light which is called waning until we get back to the New Moon phase. Phases include; New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Third or Last Quarter, and Waning Crescent. The Moon will rise about 50 minutes later each day. Full Moon is always opposite the Sun which would be setting as the Full Moon rises.

When the Moon is at the New Moon phase, it is between the earth and the Sun and this could produce a Solar Eclipse. When the Moon is at the Full Moon phase, the earth is between the Moon and the Sun and could produce a Lunar Eclipse by producing the earth’s shadow across the Moon. These lunar positions do not always cause an eclipse because the Moon also moves an angle of 5 degrees up or down to the Earth-Sun plane. Only when the Moon is at the “line of the nodes” or in alignment with the Earth-Sun plane will eclipses be possible.

This picture simply shows the 5 degrees out of alignment the Moon can be for eclipses. The distances and angles are exaggerated. The line of the nodes is the Earth- Sun plane.

The Moon is often seen in the daytime as well. From new Moon to Full Moon the Moon is rises in the daytime starting at the new moon phase and that lasts until the Full Moon phase where the Sun sets as the Moon rises. The waning phases have the Moon rising in the night time. As the cycle is completed, it starts over. Luckily, we get the Moon at the “line of the nodes” or perfect alignment with the Earth-Sun plane on August 21, 2017,which will produce our fantastic Total Solar Eclipse. Eclipse Corner will present more astronomy facts to get you ready for the eclipse. –Dan Slais

Join us August 18-21, 2017 for Midnight at Noon a four day music festival and eclipse viewing event.  For more information visit our website at 

Thursday, June 8, 2017

2017 Eclipse Corner #1 - The Energy of the Sun

2017 Eclipse Corner #1          The Energy of the Sun

The Sun is a star which has enough mass to produce gravity that will pull a whole system of objects around it. Quite a bit bigger than the earth, 1,300,000 earths could fit into the Sun. Our solar system includes 8 planets, several sub-planets, asteroids, comets, meteors, dust and gas. The Sun actually contains 99.8% of the system’s mass. The Sun fits in a package of stars we see in our night sky that range from blue to red in color. The more massive stars produce more heat and have the color blue. The smaller mass stars are less hot and are red. Our Sun as you have seen is yellow and considered an average size star. It is true, blue is a hotter color than red. A red electric stove burner can be very hot but a blue burner would melt the pots and pans.

If you have not seen different colored stars, here is a good place to look in February – the constellation Orion.  Orion, the hunter, will be slightly tilted in the east –southeast in February. Rigel is a very big star exhibiting the color blue. Betelgeuse is at a different stage in star development, but exhibits the cool color of red. It’s fun to look for the color of stars.

The Sun contains an enormous amount of energy we see and feel as heat and light. What produces this star energy? Early man compared it to a fire, but who is throwing all the wood on constantly?  Since the 1920s, astronomers believe this is nuclear energy. There are two kinds of nuclear reactions. Fission is splitting the atom which is what we did in building the atomic bomb and in our nuclear power plants of today. Fusion is combining atoms. This is what the Sun does. Man is still working on providing energy by Fusion.

The fusion reaction begins because of a massive squeezing effect of the gravity of all the mass of the Sun. The Sun is made of hydrogen and helium. Basically, the Sun’s gravity pushes 4 hydrogen atoms together to become 1 helium atom plus a little left over which produces the heat and light of the Sun. Astronomers believe this fusion reaction will keep “burning “ hydrogen for another 5 billion years.
Our Moon looks to be equal to the size of the Sun, but the Sun is 400 times greater than the Moon. The Sun is just 400 times farther away than the Moon. Therefore, we have the opportunity to witness that most amazing of spectacles, the Moon completely blocking out the site of the Sun, a total eclipse of the Sun.  Future Eclipse Corners will show you more about astronomy and the upcoming total Solar Eclipse coming on August 21, 2017.           –Dan Slais

Join us August 18-21, 2017 for Midnight at Noon - a 4-day Music Festival and Eclipse Viewing Event.  For more information visit our website


     Part of the experience of seeing the total solar eclipse is to be in the right place at the right time. With all the information provi...