Get closer to the Moon without leaving the Earth

"Close to the Moon, but not as close as I can be" - Astronomy Koan by Daniel Cummings
Astronomy Koan by Daniel Cummings

How close can I get to the Moon while still staying on the Earth’s surface?

I frame this as a sort of astronomy poem I call an Astronomy Koan. These are short sayings that contain astronomy puzzles. The answers to these puzzles carry insights into physical astronomy concepts.

Guy Ottewell has posted an article at UniversalWorkshop.com about getting close to the Moon. https://www.universalworkshop.com/2022/12/11/how-to-touch-the-moon-almost/

“I am close the the Moon but not as close as I can be.” This Astronomy Koan invites the reader to consider all of the ways which an Earth-bound observer might get as close to the Moon as humanly possible – without leaving the surface of the Earth.

The Earth and Moon are moving, I am moving

The Moon and the Earth are two oblate spheroids interacting in complex ways.

The Earth-bound observer is able to move around on the surface of the Earth while we calculate the “closest” point of the Moon to be the surface point that is closest to a surface point on Earth.

The goal of the Earth-bound observer is to find the location and time where they will be physically closest to the Moon.

Motions of the Moon that bring the Moon closer and further to your “closest personal point”

  • Daily apparent revolution – every 24h 50m wherever we are on the Earth surface, the Moon transits (crosses the meridian) and reaches the “closest personal point” at that time. 
  • The apsides of the Moon’s orbit – the Moon’s orbit is slightly elliptical and has an apogee (furthest point from Earth) and a perigee (closest point to Earth). If a perigee coincides with a Moon transit, this brings the Moon even closer to the surface of the Earth. Approximately 357000km (perigee) and 406000km (apogee)
  • The inclined orbital track of the Moon. Close to the ecliptic, but an additional 5 degrees offset, this gives the Moon an opportunity to be closest to people located on the surface of the Earth who are slightly north (up to 5.14 degrees) of the Tropic of Cancer and south of the Tropic of Capricorn.
  • The Moon’s orbit is slowly moving away from the Earth (by 3.8cm per year, about 38km in 1million years) – so the longer you wait, the further away it will be!
  • Surface of the Moon orientation toward my location – East-west libration moves the “orientation” of the Moon as it relates to the Earth
  • The surface of the Moon has crater walls and valleys. The closest point would be at the height of a crater wall or central peak. Hipparchus crater or Triesnecker crater seem like likely candidates because they are “central”, but this is beyond my understanding of the topology of the Moon surface and how it might interact with the orientation changes caused by libration, nutation, and the inclined orbit.

My motions on the Earth that can get me closer to the Moon

  • The transit can be made closer by moving closer on the surface of the Earth to the current declination of the Moon. Generally speaking, that involves going toward the equator, but it get complicated by the fact that the orbit is inclined to the equator and ecliptic.
  • The transit can be made closer by going to a higher elevation 
  • The transit can be made closer by going to the top of a mountain close to the equator (Mt. Chimborazo as opposed to a tall mountain like Everest that is not near the Equator)

The “ideal” situation that would bring a human on the surface of the Earth as close as can be to the Moon would be

Stand at the top of Mt. Chimborazo, at the moment of Moon transit, at the exact orbital perigee, with Hipparchus crater wall oriented toward Mt. Chimborazo, as soon as possible!

Summary

We looked at all of the ways that the Earth and Moon approach and recede from each other. The goal is to understand more directly when I am close to the Moon and observe the motions that change that distance.

Please let me know if I have missed anything here! Add in comments below.


References:

NASA Moon page: https://svs.gsfc.nasa.gov/5048 – has “an animated diagram of the subsolar and sub-Earth points for 2023” Indicates the general sweep of the “closest Moon-Earth point” as it traces out irregular shapes on the surface of the Moon.

NOAA answers a question about the “tallest” mountain, Mt. Chimborazo: https://oceanservice.noaa.gov/facts/highestpoint.html

ASC page with information about the various motions of the Moon: https://www.rasc.ca/motions-moon

Wikipedia Orbit of the Moon article: https://en.wikipedia.org/wiki/Orbit_of_the_Moon

Wikipedia Lunar Distance (measure the distance from the center of the Earth to the center of the Moon): https://en.wikipedia.org/wiki/Lunar_distance_(astronomy)

Moon orbit distance growing: https://astronomy.com/magazine/ask-astro/2022/08/ask-astro-how-quickly-is-the-moon-moving-away-from-earth

Quora Answer that mentions Mt. Chimborazo: https://www.quora.com/Where-on-Earth-is-the-closest-point-to-the-Moon

GPS uses Quasars

GPS uses Quasars to work

GPS uses quasars to get its own position
GPS satellite in low Earth orbit. Credit: NASA artist’s impression
The Global Positioning System (GPS) is precise.

That precision originates in a mind-blowing place!

GPS signals tell billions of people where they are each day.

GPS helps pilots land planes and captains steer ships.

GPS signals stamp locations onto millions of photos per minute.

GPS gives you driving directions.

But, where does GPS get its own GPS?

The GPS for GPS

How does GPS know where a GPS satellite is?Click here to continue reading…

Do Stars Move?

Dalle-2 Generated this image of a figure standing, wondering at the cosmos. Prompt: “gentle, happy 8 year old child, standing in a sunset forest, looking through a small, glass-covered hole in the earth that has stars deep inside, digital art, unsaturated colors” – Credit: Daniel Cummings

Heliacal rising.

Sidereal time.

Take a picture of the stars before the dawn every day.

Just before dawn, while the sky is still dark, and the stars are still out.

Tomorrow, the same thing, just before dawn, while the Earth still blocks the Sun.

Galileo’s Middle Finger

Galileo’s Middle Finger

In 1737, Galileo’s body was moved from one burial place to another. During the move several of his fingers and a tooth were removed from the body. Gruesome as it seems, this was a common treatment for the bodily remains of famous people.

One of the fingers – his middle one – eventually ended up in a museum in Florence where it sits (standing straight up) on a marble plinth under a glass jar.

Galilieo’s Middle Finger. From Wikipedia – Photo by User Saliko

Galileo’s science won the day, eventually, and after much suffering. However, thanks to this wonderful museum display, Galileo also got the final word in his epic battle with the powers of the Roman Inquisition – he’s giving them the finger – until eternity.

References:

Galileo Galilei wikipedia page

Galaxy Horizon – 4/20 at Midnight

On April 20th (4/20) at midnight Earth’s horizon (in northern latitudes) lines up perfectly with the plane of the entire Milky Way galaxy. The galaxy “wraps around” our view of the sky and we can see into and through the plane of the galaxy.

Starinastar.com galaxy horizon visualization. Shows the galaxy plane lined up with the local horizon at midnight on April 20th. This happens every year.
The Milky Way galaxy lines up perfectly with your local horizon view on April 20th (4/20) at midnight each year.

At this moment when you look out around you at the horizon, you are looking into the plane of the Milky Way galaxy.

How to See the Milky Way Galaxy Plane

Look southward (and a little bit east) and you are looking toward the center of the galaxy. Look northward (and a little bit west) and you are looking toward the outer edges of the galaxy.

Why does the galaxy line up with the horizon?

Each year on 4/20 the galaxy lines up with the horizon – an “event” I call the Galaxy Horizon. In fact, this “event” occurs every day! It’s just an interesting coincidence that the alignment happens on 4/20 at midnight. Each day the galaxy lines up again with the horizon but it happens 4 minutes earlier.

Earth Map in the Sky

Earth Map in the Sky – Landforms as Constellations

Learn how to see the map of Earth in the starry sky.

Stars help us find our way. Stars are like a giant map in the sky that tells us where we are on the surface of the Earth. Sailors use them as a “map” to navigate the world. For thousands of years, the stars were stationary markers of latitude and longitude.

We are going to learn to map something new onto the sky: locations on the Earth! We can create an exciting new set of “constellations” out of the shapes of the continents on the Earth.

We live on a sphere so we can see half of the sky (a hemisphere) at any one moment. It’s easy to imagine half the Earth mapped onto half the sky. Keep reading to learn how.

A new way to experience life on a sphere. It’s an Earth map projected onto the starry sky. Image created by: Daniel Cummings

Zenith Stars

Wherever you are on the Earth, when you look straight up (toward your zenith), you might see one star, but there are a bunch of other stars within view. All of the stars you see in the sky are directly overhead some other place on the Earth. Every place on Earth has their own set of stars directly overhead – their “zenith stars.”

Look up at any star in the night sky; that star is directly over some place on Earth. There are hundreds of “faraway zeniths” up there.

World Zeniths – See the Map of the Earth in the Sky

Every star maps to a location on Earth and every location on Earth maps to a star.

If you live in the western hemisphere, you can learn to look up and “see” the land borders of the North American and South American continents visible, projected into the sky like a giant painting on a curved ceiling. You can learn to see even more landforms in the sky – you can learn to see the entire western half of the Earth projected in the sky.

Visualize Countries in the Sky

We can learn to see country outlines in the sky. The key is to imagine yourself at the center of the Earth looking out into space “through” a translucent Earth surface.

Here is a good way to visualize these countries-in-the-sky even when you are on the surface. Imagine that you can look up and see your location at the zenith.

When I do this, I see southern New York state, Long Island jutting out into the water like a long pier, and the wide Hudson River emptying past New York City. Eastward is the dark expanse of the Atlantic Ocean and low on the eastern horizon are the countries of Europe and West Africa.

Westward in the sky, I can see the outline of the west coast of the US. Then, there is a big blank space of the Pacific Ocean and a spot near the western horizon that is Hawaii.

The Map of the Earth in the Sky is Reversed

Map of Earth landforms as they map to the starry sky. Map is reversed because it is projected into the sky. The places named at the cardinal directions (N, E, S, W) are the locations where New York horizon stars are zenith stars. Image created by: Daniel Cummings

There is one odd thing about the map as you see it in the sky… it’s reversed – as if seen in a mirror! This happens because we project the map lines outward into space toward the stars. When we look at the map this way it’s as if we are “inside” the Earth looking outward.

The map of the USA covers about 58˚ of sky from east-to-west. 58˚ is about 2x pinky-to-thumb (spread out all your fingers of both hands and touch thumbs). Your left pinky tip should be on your zenith. If you are in New York or somewhere on the east coast, the right pinky tip will indicate the approximate western edge of the USA.

Physical Astronomy – Stars Map to Places on Earth

Physical Astronomy Activity Instructions to learn to see the Map of the Earth in the Sky. Faraway Zenith stars help us visualize what it is like to live on the surface of a sphere. Image created by: Daniel Cummings

Learn to see the zenith map in your sky using this Physical Astronomy technique.

Exercise 1: face south and point high in the sky.

Face south. Then, reach both hands straight up over your head and point above your head with both pointer fingers. You are pointing at your zenith. Now, bring both arms down until they are pointing one due east and one due west. You are pointing at two points in the sky that are zeniths for someone else.

When I do this exercise in New York, my left hand (the eastern) points at a spot in the starry sky that is the zenith star for someone in the country of Nigeria in West Africa. This is a location on the globe that is 6 time zones east. My right hand (the western) points at a spot in the sky that is the zenith for someone in the island state of Hawaii in the middle of the Pacific Ocean. This location is 6 time zones west of New York.

So, when I look at the eastern horizon sky I am looking at the starry sky that is already directly above a place 6 time zones ahead of me. I am looking at someone else’s zenith stars.

Exercise 2: Repeat exercise 1. But this time, face east.

Face east, point up. Now, bring your arms down and point toward the north and the south directions. This time your right hand points south and your left hand points north. Your right hand points at a spot in the sky that is over the city of Cuzco, Peru (the closest city to Machu Pichu) and your left hand points to sky that is over Yekaterinburg, Russia – the 4th largest city in Russia.

Secret! You Can See a Star That Another Person Can’t

If you do this physical astronomy exercise right after sunset, the eastern and southern zenith locations are in night, but the western and northern sky points are over Earth locations that still have daytime.

This means that you can see the star that is at their zenith, but they cannot see that star. For example, Seattle still has 3 hours of sunlight left in their day so stars are invisible behind blue sky. The city of Yekaterinburg is on the opposite side of the world and just after sunset in New York it faces the Sun and has a bright daytime sky!

We are on the night time side of the Earth and we can see the current zenith stars of Seattle and Yekaterinburg – but people who live in these cities cannot see them! They have to wait to rotate to the night time side of the Earth to see stars.

The Math – How High Up is the Zenith Map?

Guy Ottewell’s illustration from Astronomical Companion (page 8). This schematic shows how we experience the celestial sphere – the array of stars in the sky. It shows zenith, cardinal direction points, the meridian, the celestial equator, the ecliptic, and the viewer – you, in England – sitting on the globe at latitude 40˚ north, looking up at the sky. Credit: © 2016 Guy Ottewell – UniversalWorkshop.com – used with permission.

Project an imaginary map of the Earth into the sky. The map has to be the correct size so that when it is viewed from a distance it “covers” the same distances.

If a map is too close, it is just the same size as the territory. So, we have to choose the correct distance to project the zeniths. As the zenith map “projector screen” moves away from the Earth we see more of the borders of the Earth. But, at some point the distance of the map corresponds exactly to the faraway zeniths.

Our question is: “How far away from the Earth do you have to be so the landforms (like the continents) have an angular diameter that is equivalent to their “actual size” in the sky?” How far away does our imaginary zenith map USA (about 3000 miles wide) image have to be to cover 58 degrees of arc in the sky?

To answer this we need math.

The Zenith Map Distance from Earth

Earth map showing close up of Algol passing over New York City while Gorgonea Tertia approaches Washington DC. Almach is the Zenith Star somewhere near Chicago, IL. The Earth’s rotational speed at this latitude makes the stars appear to travel a little bit faster than the speed of sound. They will be Zenith Stars for a location about 800 miles west in 1 hour. Image created by: Daniel Cummings

The Earth is approximately 24,901 miles in circumference at the equator. If we can see half the sky from any point on the Earth, then we can “see” half the Earth projected onto the sky by the zenith map. That means that for 180˚ of sky we can “see” about 12,450 miles of the Earth’s surface projected into space. 12,450/180 = 69 miles. When 1 degree of arc spans 69 equatorial miles the image is “at” the correct distance.

1 Degree of Sky equals 69 Miles

So, at the equator every degree of sky covers about 69 miles in every direction. As you go towards the poles the longitude degrees (east and west) cover less and less zenith map distance, but the latitude degrees (north and south) always stretch 69 miles. Every 15˚ of sky equals about 1035 (69*15) miles.

The distance between your pointer finger and your pinky (when you hold your arm and hand stretched out in front of you) is 15˚ – so you are measuring about 1035 miles on Earth with that sky measurement. One pinky width is equal to 1˚, which is 69 miles of zenith map!

The Math – Inverse Tangent and Angular Diameter

There is a simple calculation that helps us determine how far away something needs to be to fill just 1˚ of the sky. Here we use just a tiny drop of trigonometry to discover the “tangent of 1 degree.”

The tangent of 1˚ is 0.017455. The inverse of something is when you divide 1 by the number you want to invert. So, the inverse of 0.017455 (1/0.017455) is 57.29. The inverse of the tangent of 1˚ helps us figure out the distance something has to be to appear to be 1 degree angular diameter.

This page explains how to calculate distance from a known angular size. “When an object’s distance is 57.29 times its size, it has an angular size of 1 degree.”

So, 57.29 * 69 miles = 3,953 miles away! This is how far away the “map” has to be to show you your hemisphere of the Earth map. 3,953 miles is higher than low Earth orbit (LEO) satellites (lower than 1200 miles); it’s closer than geosynchronous satellites (at about 23,000 miles); and it’s about 1/60 the way to the Moon.

So, imagine that the Earth map is projected onto a screen – an imaginary celestial sphere, shell-shaped – that is quite close to the Earth and encircles us. It shows us our Earthen landforms and the oceans beside, superimposed in the sky.

Summary

We live on a sphere. When we look at out night sky we are able to see stars low on our horizon that are visible directly above someone else – one-quarter the way around the around the world in all directions.

If you live within 6 time zones of someone that means that you share some “simultaneous sky.” Anyone living further than 6 time zones away sees a completely different sky – unless you can see circumpolar stars that dip under the North Star. That means that you can see countries past the North Pole and down the other side of the globe.

Your zenith is yours – it is unique and changing all the time. Not even someone standing right beside you shares your zenith. You can use this idea of the zenith stars to comprehend the vast and mysterious experience of life on a sphere.

References

A list of extreme geographic points in the USA – Wikipedia – https://en.wikipedia.org/wiki/List_of_extreme_points_of_the_United_States

Sporades – Stars Not Part of Any Constellation

sporades definition - milky way behind trees; all the stars have been captured and labelled.
Milky Way behind trees. Photo by Ryan Hutton on Unsplash

Sporades definition

Webster’s 1913 Edition has this funny little entry that defines sporades:

||Spor”a*des, noun plural. [L., fr. Gr. spora`des. Cf. Sporadic.] (Astron.) Stars not included in any constellation; — called also informed, or unformed, stars.

Sporades – an obsolete word

This word no longer means anything.

This word has been removed from all dictionaries.

The International Astronomical Union (IAU) agreed in 1930 to include every known star within the boundaries of a constellation.

Sporades – the wild between constellations

Before that year there were wild places in between constellations where stars could exist. After 1930 all of the stars had been pinned down – like rows of dead butterflies. Every star is now “inside” a constellation boundary.

We don’t need this word sporades any more; all the stars have been captured.

Zodiac Wavy Charts User Guide

I want to share this amazing object with you.

It’s a skeleton key to the sky. It’s a poster. It’s a tome.

Guy Ottewell’s Zodiac Wavy Chart 2019 poster

Guy Ottewell’s Zodiac Wavy chart poster.

This poster is HUGE. 24 inches wide x 36 inches tall. Also, it’s glossy and beautiful and full of engrossing details. You will return to this poster month after month and dwell on the intricate and scientifically-accurate renderings.

It is like a Moon Calendar but it shows the actual Moon position as well as its phase and date – plus it includes everything else in the sky. Best of all, it adds the “backdrop” of the zodiac constellations so you can see how everything moves among the stars.

The Zodiac Wavy Charts poster portrays the wildness of the Moon and its dynamic motion through the sky – all in a beautiful, informative, and rewarding wall hanging.

BUY the Zodiac Wavy Charts poster here – it’s on sale!

Guy Ottewell’s Zodiac Wavy Charts is a snapshot of the calendar month. Every day’s events are “layered” onto a wavy band. Think of those wavy charts in 3-dimensions: You can pluck one off the page, stitch it together into a ring, enlarge it, and step inside it and you’ve got a view of the most interesting and active sky chart you’ve ever seen!

It’s Better than a Moon Calendar

Moon Calendar 2019

In a standard Moon Calendar the day squares contain the Moon phase images. The Moon images can be arranged artfully, but mostly they are placed to make the Moon conform to the month; the Moon gets “captured” into our cultural calendar. You can see the phase and the day the Moon phase will happen. This is good as far as it goes… but the Zodiac Wavy Charts poster is 100x better!

Guy Ottewell’s Zodiac Wavy Charts can tell you the day the Moon phase will happen. Also, it shows exactly where in the sky, and in which part of the Moon’s orbit it will happen. It tells you which part of the Moon is titled toward you, if it’s in an ascending or descending part of its orbit, and what constellation it is in.

This yearly calendar packs information that will teach you how to observe and will help you make sense of the sky. It’s like having an expert astronomer on-call all year long.

If you don’t have a Zodiac Wavy charts poster yet – you can order it here at Universal Workshop. The rest of this article will help people use the deep details on the poster to understand the motions of sky objects.

Quickstart Guide – Using the ZOD poster

Note: the Zodiac Wavy charts poster shows a northern hemisphere viewpoint. All writing here assumes you are in a northern hemisphere location.

Before you read this guide, please read Guy Ottewell’s text at the bottom of the poster. It explains many of the key items visible in the chart and serves as a legend. Guy’s writing provides a wonderful tour of the deep information revealed by these charts.

Unique Design Elements Tell the Story

The Sun’s movement in 1 month.

Guy uses clever graphic design techniques to communicate how things move in the sky. For instance, to indicate how far the Sun moves in a month he expands the Sun with concentric rings. This clearly shows the sky location on the 1st of the month (the right edge of the outer yellow ring), the 16th of the month (the central Sun image), and the last day of the month (the left edge of the yellow ring).

The Moon’s movement by day and libration.

Another unique design element (a variable-size red triangle) indicates the Moon’s current libration – tilt – towards or away from the Earth. Knowledge of the Moon’s libration helps observers see hidden Moon formations.

The Moon moves dynamically and this poster helps you really see that motion each day.

Spectral types shown on the poster.

Other things to note about the poster:

  • The stars are sized and colored to indicate their apparent magnitude and spectral class,
  • the constellation boundaries are indicated,
  • planetary retrograde motion is shown with variable-sized arrows, and
  • all solar eclipses and lunar eclipses are indicated.
The Astronomical Calendar Any Year has 20 pages of celestial events for 2019.

Guy also has prepared a detailed list of celestial events throughout the year that you can use to pinpoint on the Zodiac Wavy Charts. The Astronomical Calendar Any Year (or ACAY for short) has a FREE listing of celestial events. You can download the year’s worth of observing data in a PDF file from Guy’s website Universal Workshop.

Read the Charts from Right to Left

The Zodiac Wavy Chart should be read from right-to-left.

The Sun, Moon, and planets move (in general) from right to left across the sky. So too the Zodiac Wavy chart should be read from right to left. You can see the Moon phase images (and day numbers) grow from right-to-left. You can observe that the Sun moves from right-to-left over the month.

Sometimes when the Moon “overlaps” itself during a calendar month, the numbering looks a little funny – this happens because the calendar month is not the same as the Moon phase month (except February) the calendar month is always longer. This article about Blue Moons shows what happens when we try to squeeze the Moon into our monthly boxes.

The first and last wavy charts have lots of text indicating the constellation names, but the middle charts leave them out for clarity. If you want to find out which constellation a celestial object is “in” you can refer to the January or December charts.

Start with the Sun as the Anchor

Use the Sun as the anchor for understanding how to read the charts. Look to the left of the Sun image in each month. The space spanning 6 constellations to the left (east) of the Sun shows you the night sky at sunset. The space spanning 6 constellations to the right of the Sun shows you the pre-sunrise sky. The midnight sky is always centered about 6 constellations to the left of the Sun. You can imagine the whole of the night sky by centering your eye on the anti-Sun which shows the location of midnight on the 16th of the month.

The Sky at Midnight – Anti-Sun and the Full Moon

The anti-Sun indicates the meridian (the middle of the sky) at midnight. The anti-Sun also moves from right-to-left through the sky. It could be displayed with the same-sized concentric Sun rings. It marks midnight and you can see that the Full Moon is always close by.

Tilt the Poster to Line Up with the Sun

Here’s a fun idea: turn the poster sideways and place it on an east or west wall at sunset to “see” the star band lined up with the rising “anti-sun” (east wall) or the setting “sun” (west wall). Anchoring to the Sun or the Anti-Sun may help you visualize how the Zodiac Wavy Charts poster shows you the whole sky of Zodiac constellations all at the same time.

Why is it Wavy?

Why is the wavy chart wavy? It’s because of the way the ecliptic is tilted from the equator.

The meaning of the waves. It’s easier to imagine this if you think of the Equator as the horizontal and the plane of the solar system as tilted.

Eclipses – Every Six Months in the Same Sky

The location of eclipses = the location of node crossings = the location of the nodes = changes very, very slowly (18 years, 11 days, 8 hours to be exact).

Look at the eclipses – there are a few of them every year and 2019 is no exception! Notice that they all occur during the New Moon or the Full Moon and that they all occur in the constellations Gemini or Sagittarius. The reason the eclipses happen while the Moon or the Sun are in Gemini or Sagittarius is because of the Moon’s orbital nodes. These nodes are “in” these two constellations this year.

It’s not just the Moon that orbits the Earth, the Moon’s orbit nodes themselves actually orbit the Earth. This orbit of the nodes takes 18.6 years! The intersection with the lunar phase cycle and the orbit of the Moon’s apsides is the source of the famous Saros interval – where 2 similar eclipses occur.

So, if you buy the Zodiac Wavy Chart poster for the next 18 years, you’ll see the Moon’s orbital nodes – the location of eclipses – move through each of the fixed constellations!

Retrograde Motion – See it!

Planet motion is cool. Planets close to the Sun never cross the anti-sun, but outer planets do. This confused our ancient ancestors who did not realize that the planets were following an orbital path around the Sun at the same time that the Earth was following its own orbital path.

These two motions (the planet’s and the Earth’s) made it look like the planets sometimes moved backwards (retrograde)! You can find all of the retrograde motions easily and see exactly when and where they will happen.

Measurement – by Counting Constellations

Degree marking – the charts lack any of the standard degree measurements (Right Ascension/Declination or Altitude/Azimuth). This type of measurement is not really necessary for general use of these charts. This is because you can find these measurements in other places.

However, you may want to understand how big each section of the sky is compared to each section of the chart. You can think about it like this: there are 12 zodiac constellations (13 if you count Ophiuchus) and they span 360 degrees of the sky. We can see a bit less than 180 degrees of the sky at any one time so that’s about 6 visible constellations! Just count about 6 constellations and you’ll get about half the sky!

If you divide 360 degrees by 12, you get 30 degrees. So, an average constellation covers about 30 degrees of sky. And the sky moves at a rate of about 15 degrees per hour. That means it will take about 12 hours for the sky to completely change.

Want to figure out how big something is? Use your outstretched hand as a measuring tool. The distance from your thumb to your pinky (when your hand is fully-stretched out) is about 25 degrees – a little less than the average constellation width.

Analemma-ish

A subtle analemma appears.

One interesting after-effect of rendering the Sun’s position in this “wavy” way is that you can see an aspect of the analemma. The slight movement in the Sun’s position month over month traces a very slim half-analemma shape across the poster. There is a very slight speed up and slow down that you can see if you look closely.

Here is an image of the poster showing the slight but noticeable curve that the Sun makes.

Sidereal Map – the Stars Stand Still

These Zodiac Wavy Charts create a sidereal map of the sky. Sidereal refers to the fact that the background of stars remains fixed through every chart while all the other objects move through them.

What do you see?

There are hidden treasures all through this gorgeous image. Share them with us when you find them!

Frequently Asked Questions

  • Why is the Zodiac Wavy Chart wavy? The charts are wavy because Guy wanted to show what was happening at the ecliptic. The ecliptic is tilted at 23.4˚ from Earth’s pole (90˚ from the equator). So, sometimes objects in the ecliptic are below the equator and sometimes they are above it.
  • What is the Zodiac? The zodiac is the collection of constellations that define the ecliptic. The zodiac constellations define a band of sky where the Sun, Moon, and planets can always be found. Fun fact: Zodiac comes from the same root word that Zoo does – and it’s called that because many of the constellations are animals.
  • Is this an astrology tool? No, this is a visual astronomy tool. Astrologers will certainly find this a useful poster to refer to, but it is designed for visual astronomy observation assistance.
  • What can I use this for? This astronomy poster is useful for many things! Mostly, it’s a beautiful wall hanging that will draw your eye and reveal the deep celestial mechanics behind our Earth’s motion through the solar system each year. It’s also a wonderful conversation piece. Try telling people “It’s like a Moon Calendar, but it works for everything else in the sky too!”
  • Can I order this Zodiac poster internationally? Yes – you may have to pay a little extra shipping and sometimes customs duties, but the poster can be shipped almost anywhere.
  • Does the site accept purchase orders? No, Universal Workshop does not accept purchase orders. You can pay by credit, debit, or paypal.
  • Can I order a 2020 poster now? Yes! Please contact Guy [at] Universal Workshop [daht] com or visit UniversalWorkshop.com and make a comment on one of the recent blog posts.
  • Can I order in bulk? Yes! Contact Guy Ottewell for details.

References

NASA Saros page – https://eclipse.gsfc.nasa.gov/SEsaros/SEperiodicity.html

Precession of the apsides – https://en.wikipedia.org/wiki/Apsidal_precession

10 ways to wear a Moon Hat

Wear the Moon Hat – have fun!

The Moon Hat is no ordinary hat. 

The Moon Hat keeps your head warm – yes!  And, every day it gently reminds you to be curious about the Moon. It reminds you to observe what usually stays hidden. It reminds you to #doscienceeveryday.

There are many ways to wear a Moon Hat. You can wear the Moon Hat in at least 10 different ways. The Moon Hat is made of soft stretchy fleece with small embroidered Moon phase images placed all around the brim.

The Moon Hat fabric is flexible and foldable.

10 ways to wear the Moon Hat

  • Moon Finder – where is the Moon right now
  • Phase Reminder – what is the Moon phase right now
  • Hidden Moon outside – hide the moons outside
  • Hidden Moon inside – hide the moons inside
  • Tidal Shores no tag – longshoreman style
  • Tidal Shores show tag – longshoreman style
  • Moon Slouch – Moon Finder, pull the fleece backward
  • Moon Beret – Moon Finder, pull the fleece forward
  • Moon Disk – Hidden Moon inside, show one embroidered disk
  • Moon Peeker – Hidden Moon inside, peek one embroidered disk
  • Halfsies (Bonus #11) – Hide half the phases, wear the hat straight

#1 – The Moon Finder

The Moon Hat style The Moon Finder. This is the standard style for wearing the Moon hat. The phases are oriented in the correct way and you can face the Sun and find the Moon using the Moon Hat moon phase images.

The standard way to wear the Moon Hat with the new Moon image in front. This creates the model of the Moon, Earth, Sun relationship and helps you understand how the motions of the Moon create the phases that we see from Earth.

Get the current Moon phase. Put the hat on with the New Moon image on your forehead. Face the Sun. Now, all of the Moon phase images point to where the Moon is in the sky. Amazing!

#2 – The Phase Reminder

The Moon Hat style The Phase Reminder This is another standard style for wearing the Moon hat. The current phase is oriented to the front and you can face the Moon and find the Sun using the Moon Hat New Moon phase image.

This everyday style is for people who want to remind themselves of the phases of the Moon and how they change over the 29 and a half days of the cycle. Just choose a Moon phase and put it at the front.

This is a subtle way to keep track of the Moon phases and learn their sky location. Before you put on the hat, pause for a second and consider which phase to wear. And, it doesn’t feel like a Moon phase quiz – it’s fun to put your thinking cap on!

#3 – Hidden Moon outside

Man wearing the Moon Hat hiding all the embroidered images of the Moon Phases. Sometimes you just want to wear a cap.

Don’t want any Moon phases to show? Just fold up the brim toward the outside of the hat and all of the Moon phase images disappear.

Sometimes a hat is just a hat.

#4 – Hidden Moon inside

Moon phase images are all hidden by folding the brim of the Moon Hat inside the hat. It gives a slightly exotic look to the cap.

Another way to hide the Moon phase images… tuck the brim of the Moon Hat towards the inside. All the Moon phase embroidery is now hidden and you have a sleek cap.

Looking for a unique style? The Moon Hat is flexible.

#5 – Tidal Shores no tag

The Moon Hat style the Tidal Shore No Tag - the hat starts inside out and the brim is folded up to reveal the images. This is another standard style for wearing the Moon hat. The New Moon image is oriented to the front and you can face the Sun and find the Moon using the Moon Hat New Moon phase image.

This is the longshoreman style. Turn the Moon Hat inside out and then fold the brim outward. The brim should be wide enough to both show the Moon phase images and hide the instruction tag.

A close-fitting style that uncovers your ears.

#6 – Tidal Shores show tag

The Moon Hat style the Tidal Shore Show Tag - the hat starts inside out and the brim is folded up to reveal the images. This is outre style for wearing the Moon hat because the tag is showing. The Full Moon image is oriented to the front and you can face the Full Moon and find the Sun using the Moon Hat New Moon image.

Just like the Tidal Shores no tag, but the brim of the hat is folded thinly so that the tag is revealed. You can wear the tag on the side, or the back, or if you are feeling daring, on the front!

This style makes a strong statement – show off the instruction tag.

#7 – Moon Slouch

Man wearing the Moon Hat in slouch style. The hat is loosely bunched and then pulled backward to give a relaxed ring of Moon phase images that are carried above the ear.

This is the Moon Finder style, but pull the Moon Hat upwards to get some amount of fabric standing up away from your head and then pull it backward and flatten it for a sleek look

You can easily wear the Moon Hat pulled up above your ears.

#8 – Moon Beret

Man wearing the Moon Hat in beret style. The hat is loosely bunched and then pulled forward to give an intense ring of Moon phase images that are carried above the ear.

This is the Moon Finder style, but pull the Moon Hat upwards to get some amount of fabric standing up away from your head and then pull it forward and flatten it for an intense look.

Folding and bunching the fabric in the hat leads to a renaissance or jester look.

#9 – Moon Disk

A single Moon Phase image shows at the back of Man's head but hiding all the other phases.

The Moon Disk style starts with the Hidden Moon inside, but then you pull the embroidered disk of your favorite Moon phase and place it somewhere – it could be centered on your forehead or placed round the side of your head just behind the ear, or all the way at the back. It’s your choice.

This style lets you show an individual Moon image disk.

#10 – Moon Peeker

This is the same as the Moon Phase disk, but more discreet. Just a tiny Moon phase image disk peeks out from just in front of the right ear.

This style is the same as the Moon Disk, but pull the Moon phase under the fabric of the brim until it is just peeking out. This style looks particularly good when the disk is just in front of your left or right ear.

This look makes a sly statement.

#11 – Halfsies 

Half the Moon Hat brim is folded upwards to hide a set of embroidered moon phase images. Hat is adjusted to make it look symmetrical.

Fold down half the Moon Hat brim to hide 4 of the phases, then adjust, and angle the hat so that it looks like it is sitting flat on your head.

An alternative way of hanging your hat.

Go out and play with the Moon Hat

This is a fun and flexible bit of fabric with lots of science and a mountain of style potential. Hide and show the Moon phase images, fold and flex the fabric. Get outside and get curious about the Moon and its motion.

Lights All Askew in the Heavens … But Nobody Need Worry

Lights all askew in the heavens…

Lights all askew... The hilarious headline provided by the New York Times after Einstein's relativity theory proved based on Arthur Eddington's eclipse observations in 1919. Lights all askew in the heavens. Men of science more or less agog over results of eclipse observations. Einstein theory triumphs. Stars not where they seemed of were calculated to be, but nobody need worry. A book for 12 wise men. No more in all the world could comprehend it, said Einstein when his daring publishers accepted it.
New York Times headline about Einstein’s theory of the curvature of space time.

This hilariously-headlined New York Times article describes the results of the observational experiment performed during the 1919 eclipse. It highlights that the expedition proved Einstein’s prediction. But the writer claims that only 12 men on Earth can really understand the result: that light’s path is curved by space time.

The delightful headline reads:Click here to continue reading…

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