You've only got you Eyeballs. What can you see?
This article covers the things you can see without equipment, from anywhere - even the bright skies of the city.
The Sun
When is the only time it's okay to look at the sun without eye protection? At night.
Never look at the sun without eye protection. NEVER look at the sun through binoculars or a telescope without proper solar filters. You will get instant permanent eye damage.
We're all familiar with sunrises and sunsets.
Where do they occur?
Directly East and Directly West?
Or do they vary?
Is there a pattern to where it rises and sets?
Do the times vary?
Does every day have exactly 12 hours of daylight?
If you were isolated from the rest of the world but had a wristwatch that you wanted to set accurately, how would you do it?
Does the Sun pass directly overhead?
What time does it pass closest to overhead?
What direction from directly overhead does it pass? How far? Why?
If you were to watch over the course of year, would you see any patterns?
For viewing the sun with a properly-filtered(!) telescope, see: Solar!
The Moon without Instruments
Have you ever really paid attention to the Moon?
It's visible for say, 24 out of 28 days. When it passes near the sun every orbit, it's hard to see, but otherwise it's somewhere.
Where is it?
What direction does is travel if you watch it over the course of an hour?
If you watch it the same time for a couple of nights in a row, what direction does it appear to go? By how much?
In what direction did it rise today? Directly East? In what direction did it set? Did it rise and set in the same place as the sun or from somewhere different?
If you watch it over months does is rise from the same point on the horizon and set at the same point on the horizon? Does it vary? A lot? Does it mimic the sun? Is there a pattern?
The Dark Side of the Moon
You already know this, but not all of the Moon's face is visible most of the time? You've seen the pattern and can probably describe the pattern.
Why the pattern?
Around what time of day does the Full Moon rise? You know this. What time does it set?
The half moon that you see in the afternoon and evening (called the First Quarter Moon), what time of day does that rise? What time does it set?
There is a Third Quarter Moon. Have you seen it? When does it rise and set?
The Far Side of the Moon
Have you looked at the moon's face? It's not uniform, there are markings, patterns, right? The Man in the Moon? Does the pattern change (other than being lit up or not)?
The Moon is a sphere, right? Everything spins, right? (Trivia: the slowest rotating object we know of in the Universe is... ...Venus). If the moon is a ball and it's spinning, why do we always see the same side?
Sketch it!
The Moon is arguable the only object in the heavens you can sketch without looking through an instrument (granted, from a dark sky you can sketch The Milky Way).
Sketching is a practice that is very effective in training your eye and your mind to be a better observer. Your sketches may or may not be worthy of keeping, but you will see more detail through a telescope if you learn to sketch.
The Planets without Instruments
All the objects in the Entire Universe are fixed in place relative to each other. Consider the term "the Firmament": it is unyielding, unchanging, firm.
The Earth spins causing the universe to appear to move. But it doesn't.
Except...
- The Sun (relative to the firmament)
- The Moon
- The Planets
- Comets
- Asteroids
- Artificial Satellites
There are Five Planets of Antiquity:
- Mercury
- Venus
- Mars
- Jupiter
- Saturn
Known since antiquity? Why? Because THEY ARE BRIGHT! They are brighter than the brightest stars. They are visible from even the brightest city skies! And THEY MOVE!
So, for centuries without telescopes and televisions, you have only stars & constellations, The Sun, The Moon, The Miky Way, and the Five Planets for night time entertainment. And Astrology to weave stories during the day.
What about the other two Planets?
Uranus is small and dim, but visible in "backyard telesecopes" as a very small blue-green fuzzy disk. It wasn't discovered until telescopes were invented and one gentleman, Wilhelm Herschel, started systemically sweeping the sky with some self-made reflecting telescopes (the largest in the world at the time). When in 1781 he stumbled upon a “curious, diffuse star” that was “visibly larger than the rest,” he discovered the first planet not known since antiquity and established his name in the firmament of astronomical history. He is a rock star.
Neptune was discovered by math in 1846. By calculating "irregularities" in Uranus's orbit, Le Verrier had discovered a planet "with the point of his pen". Neptune was discovered [1] less than an hour of searching and less than 1 degree from the position Le Verrier had predicted. Except in the largest of telescopes, Neptune looks like a blueish star rather than a disk.
Planets Wander
Not only are the planets Bright, they move around the sky. Predictably, but they wander. "Planetes" is Greek for wanderer.
So they're bright and they're dynamic, so they're a big deal. Astrology talks about how the Sun and these bright wanderers determine your life. It's nonsense, of course, but you see their social influence...
Because they're bright, you can see them without instruments, even from city skies. Because they're bright, you can see great detail with instruments, even from city skies.
Without instruments, no detail is visible, other than their brightness varies by their position relative to the Sun and the Earth.
Here are the brightest objects in the heavens (at their brightest):
- Sun
- Moon
- Venus
- Mars
- Jupiter
- Mercury
- Sirius (star)
- Canopus (star)
- Saturn
Mercury and Venus
Because Mercury and Venus orbit inside of Earth's orbit, they never get far from the Sun. Mercury, while bright, never gets far from the sun and is visible only near sunrise and sunset. It's easy to not notice Mercury. Venus swings farther from the Sun and is VERY bright. You've noticed it. You've thought "wow!" while looking at it. It's often called the Morning Star or Evening Star.
Jupiter and Saturn
Jupiter and Saturn, without any instruments are not particularly interesting compared to Mercury and Venus, although Saturn has an unmistakeable orange tint. Because they orbit outside of Earth's orbit, they wander the whole sky. Not randomly because their orbit lies in nearly the same plane as the Earth's orbit (known as The Ecliptic). They do not stray far from the path of the sun through a narriow stretch of the sky known as the Zodiac.
Because of Earth's orbital motion, which is faster than theirs, their apparent motion is mostly "driven" by the Earth's. Jupiter and Saturn (and Mars and other objects orbiting outside the Earth) appear to move from East to West across the sky if you were to watch them every night. Jupiter just passed in front of Saturn on December 21, 2020 as it does every twenty years. It's closer, so it orbit's faster. The Earth continued racing east, so they appeared to move west "behind the sun". They are currently early morning "stars". Over the course of the next year, like every year, you will see them both move west, rising earlier and earlier. In a few months, they'll be rising at a reasonable time and you'll be able to see them wander west across the evening sky until they disappear behind the sun again. Jupiter leads the pair and will get further ahead of Saturn until it appears to start chasing it in 10 years for another conjunction in 20.
Mars
Mars is very orange.
Mars is a bit different than Jupiter and Saturn because it orbits close to Earth's orbit. It takes 687 days to orbit the Sun, which is much faster than Jupiter and Saturn. Whereas, when the Earth ciricles back around to it's same point in space after a year and Jupiter and Saturn have moved just a little, comparatively, Mars is nowhere to be seen. Literally. It's on the other side of the Sun. We have to wait another year until it's kind of near where it was last year. "Opposition" is what we call when we're lined up and closest to an outer planet. The farther out a planet orbits the shorter the period between oppositions:
- Saturn: 1 year and two weeks
- Jupiter: 1 year and a month
- Mars: 1-year and another year and two more months!
This is why all the rockets to Mars all launch within a few weeks of each other every 26 months: there's a short window when the flight is short and a long window when the flight is a LOT longer.
Visually, this makes a big difference in brightness. At opposition (when it's closest) it's brighter than all but the Sun, Moon, and Venus. As we get farther away from it, it dims down to well below most of the brighter stars.
In a telescope, details are only visible for a couple months out of every 26. Most of the time it looks like Saturn without rings.
Satellites!
Like the stars, satellites are always up. Like the stars, you can't see them in the daytime. Unlike the stars, you really can't see them in the middle of the night.
Satellites are visible as steadily "moving stars" after sunset or before sunrise: when the sky is dark but they're still in sunlight. Most are fairly dim, but some will catch your eye, "Is that an airplane?" Large ones can be very very bright (like Venus-bright). On any given night, if you're looking - especially from a dark site - you can see some satellites.
Satellites orbits are predictable. The orbits and flyby times of large sattelites like the International Space Station (ISS), the Hubble Telescope and others are listed online and via apps. Some phone apps can tell you when and where to look to see the ISS and other bright satellites.
Comets!
Finally: comets. Comets (and asteroids) visible to the naked eye, in the city or from a dark sky, are rare events. But they happen. And they're a big big deal:
- They're rare.
- They're very often a surprise that they're even there - they're being discovered regularly. Most remain invisible, but some come close to the earth and/or sun.
- Some rare ones are bright even in an urban sky! Hale-Bopp in 1995 was big, bright, and visible for months with the naked eye. The best comet in decades, by far.
- They behave unpredictably. Their orbits can be quickly calculated and estimates made to their brightness, but a lot of factors work to make them a dud or a delight.
- We don't really know what we'll see until we see it.
- Some move quickly across the sky (over days or weeks).
On any given night, large telescopes from dark skies can make out a known asteroid (as a "star") or a comet (generally a tail-less fuzzy star).
But, bright, naked eye comets make the news. You'll hear about them.
Stars
Almost no city is so big and the air so filthy that no stars are visible at night, but the bright lights of the city are like the light of the sun or the moon: they wash out the dimmer objects. The brighter the sky, the few stars you can see.
In most cities, you can make out the brightest stars. As the cities get smaller or you get farther away from them, you see more stars. Bright constellations and asterisms (star groups (like the Big Dipper (which is not a constellation))) become visible. Constellations were "invented" by establishing patterns to the brightest stars. As the sky gets darker, more stars become visible, filling out the bright constellations and revealing the more subtle ones. Eventually the so many stars may be so bright that it's hard to make out the constellations because there are SO MANY STARS. And The Milky Way. But not from the City. Get out of the city if you want to actually see the sky.
Once you get to a dark sky, you can see some "Deep Sky Objects". You can see the Orion Nebula, the Andromeda Galaxy, some Globular Clusters (100,000+ stars in a ball), but mostly as "faint fuzzies." The Andromeda Galaxy is 3.1 million light years away, the farthest thing you can see with your eyes.
If you have binoculars, the universe opens up to you. A small telescope will show even more. At this point, you need to go to another page or another hundred, because there is so much to see from a dark site. But even without equipment the sky will be stunning. At some point during the night the Milky Way will be visible. It's profound.
"Deep Sky Objects"
The literal meaning of Deep Sky Objects (DSOs) might be "beyond the solar system," but it might also mean "dimmer than we can normally see without equipment".
There are a number of DSOs that you can see with the Naked Eye.
But you have to know where to look. That's why it's good to know some constellations: Why Learn Constellations?