Tag Archives: Equinox

The Saturn Moment

by Shane L. Larson

I just returned from the 33rd annual Winter Star Party, hosted by Miami’s venerable Southern Cross Astronomical Society. Every February, for a week during the new moon, 400 amateur astronomers and their families descend on Camp Wesumkee in the Florida Keys.  During the idyllic days, we sit in lawn chairs, enjoy the gentle sea breezes, watch sandpipers running along the tideline, or beachcomb on the key front looking for pretty shells or little fishies trapped in tidepools.

Sunset over Scout Key, Florida, the site of the Winter Star Party. [Image: S. Larson]

But the real reason we are there becomes apparent as the Sun sinks over the western sea, and the black velvet of night emerges, studded by brilliant diamonds of light. The vast majority of us live our lives under the glaring lights of modern cities, and all too often we forget that the Cosmos is there, hiding behind our artificial fluorescent glow, waiting for us to remember. At the first sunset of the Winter Star Party, it all comes roaring back and you remember what you’ve been missing.

The Milky Way rises over Scout Key around 3am in February. You can watch a timelapse movie of the whole night, including the rising of the Milky Way, on YouTube. [Image: S. Larson]

People often ask me, “are you religious?” My answer is that I am not in the sense of modern churches and institutions, but I do know that we are part of something larger — a Cosmos infinitely vast and wonderful and intricate beyond anything we can imagine or will ever know. The cathedral of night is my church.

In his poem “When I Heard the Learn’d Astronomer,” Walt Whitman espoused the idea that you don’t need sages to know a deep connection to the sky, only the solitude of the night.

When I Heard the Learn’d Astronomer 
by Walt Whitman 

When I heard the learn’d astronomer, 
When the proofs, the figures, were ranged in columns
     before me, 
When I was shown the charts and diagrams, to add,
     divide, and measure them, 
When I sitting heard the astronomer where he lectured
     with much applause in the lecture-room, 
How soon unaccountable I became tired and sick, 
Till rising and gliding out I wander’d off by myself, 
In the mystical moist night-air, and from time to time, 
Look’d up in perfect silence at the stars. 


But in today’s fast paced world, driven by small screens, instant communication, and more information than has ever been gathered by a civilization before, it is hard to slow down enough to realize those moments of solitude. Living beneath the glare of our cities, there are generations of people who have never truly seen a starry sky and thus never built a deep personal connection to the night.

My telescope (named EQUINOX), on the observing field at Scout Key. [Image: S. Larson]

While the Winter Star Party is dominated by amateur astronomers who, like me, do this as often as we can, there are also a lot of people who are experiencing the dark night sky and the Milky Way for the first time. They walk among the telescopes at night, peering at a nebula here or a star cluster there, all the while being regaled with tales and facts of all that we have learned from 400 years of telescopic study of the sky.

This year, at around 4 in the morning, the Milky Way climbed up above the horizon, it’s center studded by a pale yellow “star.”  A young couple, at their very first star party, had stopped by my telescope for some quiet conversation and some views of the sky.

“Do you want to see something cool?” I swung my telescope over to the pale yellow “star” and let them peer through the eyepiece. The view elicited startled gasps, and loud exclamations of joy.

View of Saturn through the telescope, taken with an iPhone [Image by Andrew Symes; visit his blog here]

There is no way that is real!”  The pale yellow “star” was in fact not a star at all — it was the planet Saturn, a cream colored orb bejeweled by its famous ring, the ring itself narrowly divided by a thin black gap known as the “Cassini Division.”

Delivering a personal experience with the night sky is part of the promise of amateur astronomy. We show people the Moon, stars, clusters, perhaps an occasional galaxy. But nothing moves people like their first view of Saturn through a telescope. Most people who take the time to look walk away remembering that moment for the rest of their lives.

We call this “the Saturn Moment.”

More than any other far away object in the sky, Saturn looks like what people expect. They often respond to their view with incredulity, joking that it looks almost painted, or like a picture that has been taped over the end of the telescope.

The Moon often engenders similar responses, but people expect the Moon to look that way. They can see it with their eyes, and imagine craters and mountains, so they aren’t necessarily surprised by the telescopic view.

By contrast, most people have never seen Saturn, except through the eyes of space probes. The telescope somehow takes the NASA pictures we see on our computer screens, and makes it real and visceral.

At the Adler Planetarium in Chicago, you can see a “20 foot Refractor” similar to the kind used in Huygens time (left). We have it set up so you can look through it, and see the same kind of fuzzy image of Saturn he may have seen (right). [Images: S. Larson]

The first person to have a Saturn Moment was Galileo, who turned his telescope on the skies in 1609. His views of Saturn were not the greatest, as his sketches published a year later in Sidereus Nuncius show. It was clear Saturn wasn’t normal because he could make out blobs on either side. He wrote in a letter to his student Benedetto Castelli that Saturn had “ears.” It wasn’t until 1655 that Dutch astronomer Chrstiaan Huygens, using a much better telescope (though still fuzzy) was able to discern that Saturn was surrounded by a thin, flat ring.

A 57 mm diameter lens, all that remains of the telescope Huygens used to observe Saturn. Around the edge is carved a verse from the Roman poet Ovid: “Admovere Oculis Distantia Sidera Nostris” (They brought the distant stars closer to our eyes). It is an anagram, establishing the details of Huygens’ discovery of Saturn’s moon, Titan. When translated, it reads “A moon revolves around Saturn in 16 days and 4 hours.”[Image: Utrecht Univ. Museum, from APOD]

Today, ordinary people like you and me can own telescopes that would have made Galileo and Huygens swoon with envy. Technology is better, and available to everyone.

My Saturn Moment happened long ago, at a sidewalk astronomy event. An amateur astronomer invited me over to look through her “telescope” — it wasn’t an ordinary telescope, it was a spotting scope for birding that she had pointed at the sky. But what I saw blew my socks off. I was seeing Saturn, with my own eyes, and I could see the rings! Though I don’t remember it, I’m sure the rusty dot of Titan, Saturn’s largest moon, was also lurking nearby.

The ultimate result of that encounter is that today my wife and I are both amateur astronomers ourselves, and we guide people through their own Saturn Moments every year. Each moment is unique, exhilarating, and moving in their own way. Among the most memorable was several years ago, my wife had guided a young boy to our telescope to have a peek at Saturn. The view elicited a loud gasp, and the exclamation, “It looks just like a Chevy symbol!” Yep, it kind of does!

If you’ve never seen Saturn before, go to your local planetarium or astronomy club. They would love to show you Saturn for the first time. And when you’re done, tell everyone what you’ve seen, and encourage them to have their own, first #SaturnMoment, a moment of perfect beauty between us and the Cosmos.

Humanhenge — Marking Time in the Modern World

by Shane L. Larson

The other morning, when she was trying to decide what to wear for the day, my daughter said to me, “Is it cold outside?” Then, without missing a beat, she says “Never mind,” and picked up an iPhone and checked the current weather conditions. This brought to mind a vivid memory from my childhood of me asking the same question of my mother, and her saying “Go out and check!”  She had a rock on her porch; if it was wet it was raining, if it was white it was snowing, if it was hard to see it was foggy, and so on.

Far be it from me to eschew modern technology; it can do awesome things!  But it strikes me that if there is any truth about modern society, it is that it is entirely possible to live your life looking through the electronic portal of digital technology, rather than by looking out the window.

My schedule is kept by a modern calendar application, accessible from my phone. This is modern progress. Sigh.

My schedule is kept by a modern calendar application, accessible from my phone. This is modern progress. Sigh.

This was not always the case, of course.  Our forebears had to pay attention to the world, literally because it was a matter of life and death. Today, if strawberries are out of season in the northern US, no worries — your local store is shipping you some from far away, the cogs of the modern economy meeting your every whim.  But hundreds and thousands of years ago, crops had to be planted in time for the life giving rains, and harvest had to be brought in before fall frosts destroyed the yields that had to last through the winter.  Before quartz watches, before Greenwich Mean Time, and before Google Calendar, people still had to know what time of year it was.

So what did people do before the world worked on linked times and calendars? They watched the sky! The sky is filled with a regular clockwork of motions that ticks off the seconds, days, and aeons as precisely and regularly as the finest timepiece humans have ever made. The motions in the sky are a combination of the Earth’s orbital motion around the Sun, the spin of the Earth on its axis, and the fact that the North Pole of the Earth is not pointing straight up from the orbit.

One observational consequence of these three facts is that the Sun’s position in the sky changes over the course of a year. Each day it rises and sets at a different point on the horizon, and it tracks across the sky along a different pathway.  The equinoxes are the days during the year when the Sun rises and sets directly in the East and West. The solstices are the days during the year when the Sun rises and sets at the point furthest North and South on the horizon.

The ever-changing rise and set position of the Sun along the horizon can be used as a calendar. One of the most famous examples is the Shungopavi horizon calendar of the Hopi in the American southwest, shown below.  As the sunrise marches north and south along the horizon, its passage by certain landmarks indicates times of planting, harvest, and cultural ceremonies.  While you likely have no need for a horizon calendar, it can be fun to construct one via sunrise observations at your own home, like mine in Paradise, Utah, also shown below.

Example horizon calendars. The Hopi Shungopavi horizon calendar (top), and my personal horizon calendar for Paradise, Utah (bottom).

Example horizon calendars. The Hopi Shungopavi horizon calendar (top), and my personal horizon calendar for Paradise, Utah (bottom).

There are many ancient sites around the world where the rising and setting of the stars and Sun are aligned over carefully placed stones and architectural structures.  Stonehenge on the verdant Salisbury Plain, and the great Anasazi kiva Casa Rinconada in Chaco Canyon, and the Great Medicine Wheel on top of Wyoming’s Bighorn Range.  All of these sites, and many more besides, bespeak of the intimate knowledge our ancient ancestors had about the sky.

Ancient astronomically aligned sites. (L) Stonehenge, (C) Casa Rinconada, (R) Bighorn Medicine Wheel.

Ancient astronomically aligned sites. (L) Stonehenge, (C) Casa Rinconada, (R) Bighorn Medicine Wheel.

Manhattanhenge, looking down 42nd Street.

Manhattanhenge, looking down 42nd Street.

Sometimes modern landscapes align with the celestial clockwork, possibly by design but often by accident.  Consider the island of Manhattan. The island sits in the mouth of the Hudson River, canted diagonally to the north-south direction.  When it was first settled, the streets were laid out willy-nilly, in the usual haphazard organic way of ancient cities.  The expanding maze of twisty little streets that all look the same was abruptly ended by the Commissioners’ Plan of 1811, which established a grid plan for the growth of the city.  The grid was laid out with the long northish-southish thoroughfares running parallel to the coastline of the island.  As a consequence, the cross-streets running eastish-westish are all canted roughly 25 to 30 degrees to the east-west direction.  As it turns out, that is just the right tip for all the streets to be close to lining up with the sunrise and sunset directions on the Summer Solstice!  This was famously noted about ten years ago by Neil deGrasse Tyson, who dubbed the phenomenon “Manhattanhenge.”

The street grids for Manhattan (L) and for Chicago (R). The geometry of the streets determines when you will have a well placed sunrise or sunset to make a cityhenge.

But you don’t have to travel all the way to Manhattan to enjoy modern astronomical alignments.  Many towns and cities are laid out on a grid system.  For grids lined up on a north-south and east-west system, magic happens every March and every September, on the equinoxes.  For instance, in the city of Chicago, the streets are laid out (more or less) on a rectangular grid aligned to the compass points, and a “Chicagohenge” can be photographed on the Spring Equinox in March, and on the Fall Equinox in September!

Examples of Chicagohenge [Images from Ken Ilio's Uncommon Photographers].

Examples of Chicagohenge [Images from Ken Ilio’s Uncommon Photographers].

No matter where you are, there is probably an opportunity to use your city as a henge for photographing the ever-changing motion of the Sun.  Even small towns, like Vankleek Hill, Ontario.  The town is about half-way between Ottawa and Montreal, and has a population of only about 2000 people. The grid is laid out canted to the compass points, roughly parallel to the drainage from Lake Ontario into the Gulf of Saint Lawrence.  It’s just enough to line up with the Sun on the solstices, captured in this image by Gabriel Landriault.

(L) The street grid in Vankleek Hill, Ontario is canted about 20 degrees to an east-west line. (R) A summer solstice along Vankleek Hill's streets [image by Gabriel Landriault].

(L) The street grid in Vankleek Hill, Ontario is canted about 20 degrees to an east-west line. (R) A summer solstice along Vankleek Hill’s streets [image by Gabriel Landriault].

The Vankleek Hill picture hints at another point in this whole game.  The streets in Vankleek Hill are only canted 20 degrees or so from east-west, whereas the Sun is a bit farther north on the solstice, so is not perfectly aligned in this case.  But there is some day during the year when it is aligned!  This is a subtlety that was hinted at by our horizon calendars — the Sun is always on the move, marching up and down the horizon.  On the soltices and the equinoxes it is in a definite, predictable location on the horizon.  But with some careful planning, observations, and simulation (such as with a planetarium simulator like Stellarium), you can figure out when the sunrise and sunset will line up with the streets in your own town.

An example simulation of sunrise and sunset from the Adler Planetarium on the Spring Equniox, using StarryNight desktop planetarium software.

An example simulation of sunrise and sunset from the Adler Planetarium on the Spring Equniox, using StarryNight desktop planetarium software.

The truth is, it is not a life and death matter if I don’t pay attention to the daily motion of the Sun and use that information to lead a subsistence, agrarian lifestyle.  I have a calendar, the Farmer’s Almanac, and Google to tell me when to plant my snap peas.  I can really just do astronomy for fun — because it is cool, and it lets me capture some beautiful pictures that I can use to impress my friends and woo members of the opposite sex.

The Spring Equinox is just around the corner!  So go out with your cell phone and catch a sunrise or a sunset, directly down your nearest East-West street. Make sure you tweet the picture to the rest of us, so we know it is spring and can start to think about planting our gardens; strawberry season is on its way!