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Astro Mark Astro Alert: A Full Lunar Eclipse, May 15th - That’s Amore!

By “Astro” Mark Laurin, Keystone Science School Adjunct Instructor & Volunteer



Greetings Fellow Stargazer!

You’ve heard the lyrics to the Italian song, “When the moon hits the sky like a big pizza pie, that’s amore!” Of course you have. And this Sunday, May 15th, the Moon will be that big pizza pie as the cosmos serves you up a huge Italian style pie of celestial goodness. Yum.

Fun fact. Did you know that lunar eclipses only occur at Full Moons, and are visible anywhere the Moon is above the horizon at the time of the eclipse? .

The Ingredients for a Great Lunar Eclipse Pizza:

An eclipse begins with a line. Remember, a line is made up of a set of points which is extended in opposite directions. In astronomy speak this is called "syzygy"—a rough straight-line configuration of three (or more) celestial bodies in a gravitational system. You want to know more?

Eclipse lines

In a lunar eclipse, those set points are the Sun, the Earth, and the Moon. As the Earth passes between the Sun and the Moon, the Earth casts its shadow on the Moon. But, since the Moon’s orbit is tipped around 5 degrees off-plane, in relation to the Earth and Sun, that straight line isn’t entirely straight. A lunar eclipse is the result of the Moon crossing that plane of the Earth and Sun at the same time of a Full Moon.

Get a Napkin, It’s a Big Pie!

This total lunar eclipse just happens to be near the time when the Moon is closest to the Earth in its elliptical orbit. This point is called the “perigee” of an orbit. A Full Moon at perigee is often called a “Supermoon.” So here we have a “perigee-syzygy.” Whoa! That’s a lot to take in. If you need to sit down to catch your breath, that’s fine. The eclipse from start to finish will last 5 hours and 20 minutes so you have time to recover.

Eclipse anatomy

Are There Types of Eclipse?

Yes, there are three basic types of lunar eclipses:

  • Penumbral Eclipse – When the Moon passes through the Earth’s penumbral shadow. 
  • Partial Eclipse – When the Moon only partially enters the Earth’s umbral shadow.
  • Total Eclipse – When the entire Moon passes through the Earth’s umbral shadow.

Times and Events of the May 15th Eclipse:

  • 7:33pm MDT - Moon enters the Earth’s penumbra
  • 8:28pm MDT - Moon begins partial eclipse
  • 9:30pm MDT - Moon begins totality
  • 10:54pm MDT - Moon ends totality
  • 11:55pm MDT - Moon ends partial eclipse
  • May 16th, 12:51am MDT – Moon departs the Earth’s penumbra

What to Look For?

Here in the western states, the Moon will rise in the southeast already inside the penumbra. While it appears the Earth is only covering just part of the Moon’s disk, the Moon is actually entirely inside the Earth's shadow. During the partial phase of the eclipse look for the curved shape of the Earth’s shadow as it moves across the Moon. (Er, who says the world is flat?)

When the Moon enters the umbra nearing totality, around 10:12pm MDT, the color of the Moon’s surface and the rim is breathtaking. The Moon’s face can be a rusty brick red while the rim of the disk can be a bright orange. This coloring is due to both atmospheric particulates (dust, ash, sand) and to Rayleigh scattering. This scattering effect happens when sunlight is refracted and scattered by the Earth's atmosphere. The result is the longer, red wavelengths are bent and directed towards the shadow cone and onto the Moon’s surface. Don’t be surprised if you see the same red sauce color of your favorite pizza pie.

Use your binoculars or telescope to get an even bigger bite of color, appearance, and brightness. And while you’re observing the eclipse at totality, notice the sparkling background stars surrounding the Moon, and then as they slide behind it. This is called an occultation. A stunning sight. Mamma Mia!

I made a cosmic call to my favorite Italian Auntie Rosie (rest in peace) and asked if she thinks the Moon at total eclipse resembled one of her scrumptious pizza pies. She replied, “Oh, Marko, it certainly does! Mangi! Mangi!” Translated: “Eat up! Eat up!” Ah, that’s Amore. Wishing for clear skies and hoping you enjoy the eclipse!


Credits: Celestron Telescopes,, Astronomy Magazine, Sky and Telescope Magazine,, and SkyatNight