Every “spot” on Earth has a corresponding “spot” in the sky. For instance, on the spot where you are now, directly overhead, is the zenith. There is only one zenith where you stand. No two spots share the same zenith. Every spot on a sphere “points to” a different location in the sky. Nobody shares your zenith.
Your Zenith is Unique
Imagine the boundary of your country as a set of these spots. These locations can be projected onto the celestial sphere. Projecting shapes of countries onto the sky can help you really “see” how large or small a country is. Seeing countries from the inside out helps to understand the shape of the Earth as a sphere.
That Star is Someone’s “First Star I See Tonight.”
When you see a star rising you are actually seeing a star that someone 6 timezones east of you sees directly overhead.
Sirius rises just before dawn (heliacal rising) in mid August (at latitude 40˚N). It rises earlier and earlier each day until by November it is rising at midnight. When people on the east coast of the USA see Sirius rising, people in Western Europe see the same star Sirius high in the sky at the meridian.
Stand outside on a sunny day or in a room with only one light. If you are inside the light should be at eye level when you are standing up. This will be your Sun.
Stand up, make sure there is space around you – things might get messy if you start spinning like the earth and there are things to bump into.
Turn to the left and begin a slow leftward spin. This is the direction that the Earth rotates (as “seen” from above the north pole).
Your head is like the earth. Your eyes are like two different people on the surface of the earth. They are looking straight out from the earth toward the sun.
As you spin in your leftward rotation, wink your left eye shut. Observe how your left eye can see the light before your right eye. This is like the east and west coasts of the USA. The east coast is a few hours ahead. Observe how when you continue to spin and your eyes turn away from the light source it is like night.
Spin a few times more to feel yourself as the Earth model. 29-31 spins makes a month. 365 spins makes a year. Multiply your age in years by 400 and that’s about how many days you’ve been riding on the earth – give or take a few hundred.
These are the Zodiac constellations in the correct order from Aries to Pisces.
Table showing the order of the Zodiac Constellations, their names, descriptions, and emojis
Memorize the Constellations of the Zodiac in order
This mnemonic (memory device) can help you remember the correct order of the constellations of the Zodiac. This is the best way to memorize the order of the constellations of the Zodiac. It starts with Aries and ends with Pisces.
“All the great constellations look very lovely; shining, (orderly) stars creating animal patterns.”
Why does the Zodiac constellations list start with Aries?
When astrology was invented it was the same activity as astronomy – observing and cataloging sky objects and their locations) but over the years the two practices have become very different. Astrology is now concerned with how the movement of the skies affects humans while astronomy has become a science. Scientists build knowledge to make predictions about physical events.
During early astrology/astronomy times, the most important thing about the study of the stars was to know where the Sun, Moon, planets, and other solar system objects were located in relation to the steady, orderly background of stars.
Why does the order of the Zodiac constellations read right to left?
The Sun, Moon, and planets seem to move “through” these 13 constellations in order through the year. Starting with Aries, let’s follow the movement of the Sun against the backdrop of the steady stars. The next constellation that the Sun “moves into” is Taurus. Taurus is to the east (left) of Aries! The Sun appears to move into the next Zodiac constellation about once a month.
Why did we add Ophiuchus to the original 12 Zodiac constellations?
Ophiuchus is a constellation, not an astrology “sign.” However, it is an official constellation that intersects the ecliptic. So, while astrologers do not consider this a Zodiac sign, astronomers include it because the constellation is located on the ecliptic.
The Ecliptic is a path in the sky that solar system objects follow
The solar system objects move generally west-to-east in a small band of the sky – this band of sky is called the ecliptic. All the Zodiac constellations are “on” the ecliptic and all the Sun, Moon, planets and other solar system objects move along the ecliptic over time.
There is another line in the sky called the celestial equator that is an imaginary line the rises from the equator of the Earth. The celestial equator and the ecliptic intersect at a “location” in the sky.
Right now in 2020 that intersection location is “in” the constellation Pisces.
However, when astrology was created this intersection point was “in” the constellation Aries.
This was known as the “First Point of Aries.” Astronomer Guy Ottewell writes about this imaginary point in the sky on his website UniversalWorkshop.
You can learn the order of the Zodiac constellations by using the mnemonic device shown in this article. There is a pathway in the sky that the solar system objects seem to follow. It is called the ecliptic. The Zodiac constellations are the 13 constellations lined up in the sky “on” this imaginary line.
The order of the Zodiac constellations is made because of the way the Sun, Moon, and planets seem to move east-to-west past these constellations in order during the year.
We start the Zodiac names list with Aries because the Zodiac constellations were first named thousands of years ago. At this time, the ecliptic intersected the celestial equator “in” the constellation Aries.
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.
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 – 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.
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
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
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.
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?
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
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.
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.
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.
Full – we see the entire circle of the Moon lit up
Waning Gibbous – the Moon starts shrinking
Third Quarter – again only half a circle is visible
Waning Crescent – the Moon is about to disappear
New (again) – the new Moon is not visible
Moon phase names – The Moon Hat
Buy a Moon Hat (a great science gift made by Star In A Star – order today and get FREE shipping), you can learn all about the Moon phases every time you wear the hat. The Moon Hat is a scientific “moon-finder” instrument that helps you locate the Moon in the sky day or night.
The Moon Hat is one in a line of “Science Clothing – clothing that makes you smarter!” It was invented and is made and sold by Daniel Cummings – the owner of this website and the author of this blog.
Play with the Moon Phases in order from right to left
This is a “physical model” of the Moon’s phase changes. Move the mouse Right to Left.
Each day the Moon moves leftward (east) through the sky – for people looking at it from the northern hemisphere. As it moves through a 29.5 day orbit, the Moon grows and then shrinks again. It starts New, grows Full, then wanes to New again.
Move your mouse from right to left on these Moon Phase emojis to recreate the correct order of phases as the Moon moves in its orbit.
Remember the 8 Moon phases
The main Moon Phase cycle is very simple and symmetrical:
New -> WAXING -> Full -> WANING -> New.
Studying for a Moon Phases quiz?
You can shorten the Moon phase names to: “Never can quit getting food” = NCQGF
NCQGF = New, Crescent, Quarter, Gibbous, Full
Just remember that sequence of letters: NCQGF. That gives you the order of the waxing phases, then reverse it to get the waning phases: FGQCN. The good thing about this sequence of letters is that you just have to memorize it one way! During your Moon Phases quiz you can write it down and then reverse it.
You can remember wax and wane because wax is growing like putting layers of wax on something. Like in the old Karate Kid movie “wax on.”
A mnemonic – DOC – will help you learn the Moon phases names
Here’s a good way to remember the order of the Moon phases if you have to choose the phase name based on an image of the phase: DOC.
The three letter word DOC is a good mnemonic for remembering the Moon phases names and how they grow first and then shrink. It’s a “shape-ronym” – I have a feeling I just invented that name – it’s where the letter shapes help you remember something.
If the Moon phase is shaped like the letter D that means it is growing (waxing). If the Moon phase is shaped like the letter C that means it is shrinking (waning). If it’s shaped like the letter O – it is full: in between waxing (D) and waning (C).
You can remember that “light starts on the right” of the waxing crescent, then it grows to full, then shrinks to the crescent where “the only light left is on the left.”
NOTE: if you are in the southern hemisphere the mnemonic is COD because the Moon is Upside Down.
Start – The Waxing Moon D
As soon as the growing (waxing) Moon becomes a Waxing Crescent Moon we can see that the shape of the lit up part of the crescent can make the capital letter D. As the Moon grows through to Waxing Gibbous phase it is still shaped like a capital D.
Middle – The Full Moon O
The Full Moon is shaped like a capital O.
End – The Waning Moon C
The waning phases make the shape like a capital C.
Moon Phases Names patterns
Here are a some interesting patterns in the Moon phases names.
The cycles repeat – New to Full to New (again).
The Moon grows (waxes) and then shrinks (wanes) again. Why doesn’t the Moon grow to a Full Moon and then just blink out and start again… or maybe it could stay the same shape all the time… so many possibilities… why does it grow and then shrink?
The New Moon is the commonly accepted “beginning” and also the “end” of the cycle.
Gibbous is a really weird word – it is from the Latin “hunch or hump.”
There is a first and third quarter, but no 0th or 4th quarter.
Wax and Wane are more weird, old words – they are words originally handed down from the ancient language Sanskrit that made their way through history to old German and finally to old English.
The Moon’s Missing Quarters, weird
What’s the deal with First Quarter and Third Quarter?
Astronomy names can be unusual sometimes. The Moon has a “First Quarter” and a “Third Quarter”… but it has no “Second Quarter” and no “Fourth Quarter” or “Zeroth Quarter.”
The Second Quarter would be the Full Moon but we don’t use that name. But, then what would the New Moon be called? Is it the Zeroth (0th) quarter or the Fourth (4th) Quarter? Is the New Moon the beginning or the end of the orbit? Based on the more common name it should be called the zeroth quarter because it is the “New” part of the orbital cycle. Zero = nothing and during the New Moon there is no Moon visible.
The Moon is at “First Quarter” but its shape is half a moon!
This is kind of strange too: the moon looks like a “half moon” two times during the moon’s cycle. It is a half moon as it grows (waxes) and becomes a half moon again when it shrinks (wanes). The moon is clearly showing half a moon.
Confusingly, astronomers actually call the “half moon” a “quarter moon.”
Regular people call it a “half moon” even though astronomers call it a quarter moon. We should allcall the first quarter moon the “waxing half moon” and the third quarter moon the “waning half moon.” But, these are not common names at all!
Actually, I’d like to call the first quarter (waxing half moon) the “Earth’s tail moon” and the third quarter (waning half moon) the “Earth’s nose moon.” These names point out a neat fact about the Moon’s orbit – it crosses the Earth’s orbit twice a month – once at first quarter, then again at third quarter.
Anyway, why do astronomers call a half moon the quarter moon?
Astronomers use the quarters to talk about the orbit of the Moon and its location in the orbital path. The name “quarter” says “the Moon is a quarter of the way through its orbit now.”
The moon phases names are odd
How to remember the phases of the moon? Let’s face it, the Moon phases are named with really old words – the kind of words we don’t really use anymore, but we are stuck with them because the Moon is kind of important and we can’t just ignore it.
Here is a good way to think about the words tied to the phases of the Moon. These words describe 4 things: the “age” of the Moon, the apparent “shape” of the Moon, its direction of growth, and its location in its orbit around the Earth:
Age, Shape, Growth, Orbit
These words describe the “Age” of the Moon: new moon, quarter moon,
These word describe the “Shape” of the Moon: half moon, full moon, gibbous moon and crescent moon.
These words describe the “Growth” of the Moon: waxing (growing) moon and waning (shrinking) moon,
This word describes the Orbit of the Moon: quarter moon.
The light of the Sun always comes from one place – the Sun! Light from the Sun hits the Moon and lights up half of the Moon at all times.
However, it is not always the same half that we are looking at from Earth. The Moon shows us only part of its bright side for most of its 29.5 day orbit. It’s only during the Full Moon that we see the entire “half” illuminated Moon.
The Moon seems to change shape
The Moon changes phase because the Moon moves. As it moves, we see different light from the Sun reflecting off the Moon every second. The amount of light we can see changes every second as it moves through space around the Earth.
It’s a skeleton key to the sky. It’s a poster. It’s a tome.
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.
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
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
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).
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.
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 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?
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.
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.
You can see Venus in the sky at two times and locations:
in the early evening, shortly after sunset in the west or
the early morning, shortly before sunrise in the east.
Venus orbits the Sun and moves from evening sky to morning sky and back again over the course of about 18 months. Venus makes beautiful sweeping motions in the sky that reveal secrets of the solar system.
The orbits are all in the same plane. It’s like they are all marbles circling around the sun on the same giant plate. This is called the “ecliptic” and it is visible in the sky if you know how to find Venus.
Intersecting space planes
The “space plane” is not an airplane
The “plane” is a tool you can use to see the way things move in space. This “plane” is not an airplane, but a flat slice of space.
Here is an image of two intersecting planes. Imagine the blue plane is the earth’s surface and the brown plane is up-and-down from ground to sky.
Each object (and movement) in space creates a “plane,” an imaginary slice through physical space. The blue “plane” above looks like the surface of a pond, lake or ocean. A wall or roof of a house is a plane. A dinner plate is a plane. Stretch your arms out and spin in a circle and you have created a plane with your arms.
There are planes in space everywhere.
Your own personal space plane
You create a plane with your vision and balance. You can imagine a flat surface like the surface of a pool of water and your eyes are just above the waterline. This surface moves and tilts when you move your head.
Your head has two eyes that define your plane of vision. Also, your body is oriented to gravity because of your sense of balance – the “personal horizon” is the first plane for you to orient to. Your body naturally coordinates your visual sense with your sense of balance and gives us the sense of being located level on a surface. This is the “sense of horizon.”
A new horizon – choose a plane!
To get good at Physical Astronomy, we have to learn to coordinate our main “personal horizon” plane with other planes of the earth, moon, solar system, galaxy, and universe.
The earth for instance, has a lot of planes, the range of latitudes, the north and south poles, the Arctic and Antarctic circles, the equator, the tropics, a range of longitudes, the prime meridian, the international date line, the ecliptic, the galactic plane and more.
To keep things simple, let’s focus on just one other plane for now: the plane of the solar system. A wonderful thing will happen when you learn to link the plane of vision with the plane of the solar system. It’s pretty easy to do, and it’s a skill that gets better with practice.
The key to linking vision and solar system planes is to know that the plane of the solar system is visible as the ecliptic. One easy way to see the plane of the solar system is to see the bright inner planet Venus.
See Venus and the Orbit of Venus
Venus is closer to the Sun so we are able to see its entire orbit. Actually, we can’t quite see the entire orbit because sometimes it goes in front of the sun and sometimes it goes behind the sun.
We can see Venus in the early evening and in the early morning. Venus is visible in our sky when it is at the left and right extent of its orbit around the sun. We only see Venus in the sky when it is swooping around the left or right of the sun.
If you want to see the orbit of Venus and see the plane of the solar system you can do it! All you have to do is imagine a line connecting Venus to the Sun.
If you are looking at Venus early in the morning before sunrise or early in the evening before sunset, the process is the same. Imagine a line connecting Venus to the Sun; this is the ecliptic. Venus’s entire orbit covers roughly 1/4 of the sky.
We learned about two main planes in space: your personal horizon (which changes as the Earth carries you around the Sun) and the plane of the solar system: the ecliptic.
By learning to visualize these two space planes, we can begin to experience the extremely large dimensions of space.
Have you ever looked up and wondered how many stars are in the sky?
It’s a simple question with a surprising answer!
This question has layers of answers – the most common answer is “it depends” – it depends on where you are, what part of the year it is, what time it is, and most of all… how dark are your skies and how powerful is your telescope?
Let’s start with a quick (approximate) list of how many stars you might be able to see at once at night under “normal” conditions with no telescope. (The details on these calculations are near the end of this article.)
How many stars can I see at night:
The most stars anyone can see from the Earth (no telescope): 3700
The number of stars can you see at a dark sky site: 2000
How many stars can I see in my suburban yard: 200
How many stars can I see in a large city: 20
Another trick answer to “how many stars are in the sky?” is: “all of them!” All of them are in the sky, but they are just not visible to you “right now” for one reason or another.
I know, these answers are not quite what you may be looking for. Let’s look a little bit deeper by starting our search for how many stars can I see at night.
Quiz – How many stars are in the sky, how well do you know them?
Let’s start by taking a short quiz (answers are just a scroll away, so don’t peek!):
Which star is the brightest in the sky?
Which star is the closest to us?
Which star is the first one discovered to have a planet supporting life?
Which stars have a solar system?
Scroll down a bit to see the answers to this first part of the quiz.
While we are waiting to scroll (and to keep the peekers from peeking!)… let’s talk a little bit about how professional astronomers count the stars.
Annie Jump Cannon – Harvard star counter extraordinaire
Have you ever tried to count the stars? If you have, you probably gave up at some point because there were too many to keep track of.
In the early 1900s there was a tenacious Harvard astronomer named Annie Jump Cannon who didn’t give up counting! In fact, she counted so many stars that she almost lost track.
To keep everything organized she started categorizing them by their colors. She invented the spectral classification system – O,B,A,F,G,K,M – and personally classified over 350,000 stars!
Her method of categorizing stars is still in use today.
The answers to the star Quiz
The number of stars in the sky is…
SPOILER ALERT! – Here are the answers to the quiz above!
The quiz is a trick quiz because the answers to are all “the Sun.” If we don’t include the Sun in this quiz then we get very different answers and the answers are:
Sirius is the brightest star (it is almost as bright as Jupiter),
Proxima Centauri is the closest star (it is 4.22 light years away),
No star’s exoplanets have yet been proven to support life – the Sun is the only star so far to host life.
There is only one solar system. The answer to question 4 is truly a trick question: “No other stars have a solar system… because only one star is named “Sol” … the Sun! The “Solar System” is named after Sol – the Sun. See: Sol+ar = Solar. Other stars would have planetary systems named after the star. For instance, there may be a “Sirius-ar system” that hosts a planet like Earth.
The Known Universe
Ok, now you are done with the quiz let’s get counting stars. Go outside, look up, start counting!
Before, we start… There is one tiny problem with counting the number of stars. Even with the best tools humans have invented, we can only see a small part of the universe. Astronomers call this the “known universe” and it stretches about 14 billion years back through time in one direction, and (we assume) 14 billion years back in another direction.
Ten sextillion stars in the known universe
Astronomers have estimated the number of stars in the Milky Way galaxy as one hundred billion (this is a low estimate by the way). The Milky Way is an average galaxy. Astronomers estimate that there are one hundred billion galaxies in the known universe (another low estimate). The math to figure out the total number of stars in the universe is as simple as the result is mind-boggling!
Counting to one million is not like Counting to one billion
A million is way, way smaller than a billion.
It would take 11 days to count to one million if you counted one number per second without doing anything else. Counting to a billion at the same pace (one per second) would take you 32 years of continuous counting!
Count to 1 million at a rate of 1 per second = 11 days Count to 1 billion = 32 years
If you counted all the stars in the Milky Way at the rate of one per second, it would take you about 3200 years to finish counting our one galaxy’s set of stars.
How many stars in my sky now?
Ok. So, let’s get real. Now we know how many stars there may be in the entire known universe, let’s narrow the question.
Here is how we will narrow the question. Let’s create a set of ideal conditions that will guarantee we see as many stars as possible.
This is the set of almost ideal seeing conditions. This set of conditions would guarantee seeing the most number of stars that anyone could ever see with the naked eye:
I am on a tall mountain top with no trees looking up at the perfectly clear and calm sky right now. It is midnight. I can now see approximately half the stars in the sky. These near perfect seeing conditions make it so that I can see stars to magnitude 6 with my 20/20 vision.
Number of stars in the sky I see
According to David Haworth of Stargazing.net there are approximately 7400 magnitude 6 or brighter stars. Remember, we can only see half the sky at any time. So, cutting 7400 in half we get 3700 stars. 3700 stars is the greatest number of stars that any earth-bound human can ever see at any one moment without a telescope or other aides.
Stars in my sky right now
Now we know how many stars you might ever see at once, let’s look at how most people see the sky.
Most people cannot see 3700 stars because of serious light pollution, horizons full of trees and landforms, and atmosphere, lots of watery, moving atmosphere floating above us.
If you are lucky and go camping in a dark sky area you might be able to see about 2000 stars on a good night.
In a typical, light-polluted suburban sky you can see approximately 200-300 stars.
In the middle of a big city the number of stars goes down to about 12 to 20.
12. That’s not a lot of stars. Maybe take a trip out of the city to see the stars?
You can see 3700 stars under perfect viewing conditions.
You can see about 2000 under excellent dark skies.
You can see about 300 stars in the suburbs.
You can see 12 stars under bright city lights.
References for how many stars
Stargazing.net – David Haworth compiled data on the number of stars at each magnitude and presented it in a nice table.
Sky and Telescope article – covers skyglow, light measuring technology, light maps, NELM and more. Authoritative.
Space.com article – how astronomers estimate the number of stars in the Milky Way.
National Geographic Kids – Mini article on light pollution with estimates on how many stars are visible from different places.
One Day of Observation: the Sun rises and the Sun sets
Let’s start with a few easy observations about daytime. These are things you can notice just by waking up early one day before the Sun brightens the night.
The Sun starts the day for us on one side of the sky and ends the day on another side. At both of these times (sunrise and sunset), the Sun appears near to the ground – at the horizon.
During the middle of the day, the Sun appears to move “up” and across the sky and then back “down” again. In the middle of the day – at noon time – the Sun is high up in the sky, away from the ground.
Shadows change during the day
In the morning the Sun makes long shadows. At noon the Sun makes short shadows. At the end of the day, the Sun makes long shadows again.
With a few simple tools you can measure the Sun’s position and shadows.
The Sun moves east to west
Over the course of one day, the Sun appears to move across the sky from east to west, rising to the highest point at noon. The Sun’s light shines on the Earth and makes shadows that move and change position and size. As the Sun “moves” through the sky, the shadows move on the ground.
Build a simple sundial, track the Sun
A sundial tracks the shadow of the Sun with an object that casts a shadow and time markings. For the simple sundial you can use a stick. The shadow of the stick (the stick on a sundial is called a gnomon) moves across the sundial. The shadow of the stick points to the time markings.
The simplest sundial is just a stick stuck in the ground with time markers nearby. The location of the stick’s shadow moves across the time markers throughout the day.
Mark the shadow’s position with any object (chalk drawing, a rock or another stick is a good choice). In the morning, the Sun appears low in the east and the shadow is long. The morning shadow points toward the west. At midday (noon) the Sun is at the highest point so the shadow falls in the middle and becomes short. At sunset, the shadow becomes long again – pointing to the east.
Paper Plate Sundial
A paper plate with a pencil stuck through the middle makes a great moveable sundial! (Remember, when you move a paper plate sundial, you have to be careful to place it in perfect north-south alignment.)
Take this outside on a sunny day, then make a mark on the paper plate at the top of each hour. The shadow will move slightly each hour. The mark should go at the middle of the pencil shadow.
When you have completed this during one sunny day, you have made a sundial that can tell the time – roughly speaking!
An indoor sundial – the Sun Tracker
Most people think of sundials as something that you place outside. But, the Sun shines inside through windows. You can track the Sun through a window.
An indoor sundial can help you track the Sun from the comfort of your own home! Do you have a sunny (or partly sunny) window? You can track the Sun and reveal the secrets of the Earth’s motion.
The Sun Tracker is an easy-to-use indoor sundial. Place the glistening window cling on any sunny window and then mark the position of the window cling’s shadow using one of the included stickers.
Repeat the next day or the next week at the same time of day. You will see a pattern emerging: the shadow cast by the Sun moves quite a bit each day.
If you are extra precise with recording the shadow at the same time of day, and you are able to do it for an entire year… you will see the Analemma.
The Sun Tracker is like a little bit of Stonehenge for your window.
Track the Sun with simple tools and you will reveal the motion of the Earth. There are two main motions of Earth, daily rotation and yearly orbit. Earth spins under the Sun each day and around the Sun in an orbit each year.
It is these two motions that make the Sun seem to move in the sky. Remember that the next time you are looking for the Sun – it’s where it always is… the Earth is what moves.