Articles About Astronomy (111)
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/four-seasons.jpg?1)
Defining Seasons
When do seasons begin and end in the two hemispheres?
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/twilight-dubai.jpg?1)
Twilight, dawn, & dusk
Learn more about different kinds of twilight, dawn and dusk.
![The Full Moon behind three horses.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/farmers-almanac-horses.jpg?1)
Full Moon Names
Full Moons had given names in many ancient cultures. The Full Moon names we use today often reflect nature like Harvest Moon.
![Zoomed in image of the Full Moon with its surface of craters and mountains.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/full-moon-phase2.jpg?1)
Full Moon – the Moonlight Phase
The 3rd primary phase of the Moon, the Full Moon is the moment its disk is illuminated by the Sun's rays.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/total-lunareclipse1.jpg?1)
What's a Blood Moon?
A total lunar eclipse is often called a Blood Moon because of the red glow the eclipsed Moon gets. The term is also used for four total lunar eclipses that occur in a row.
![Calendar of Cosmic Events, Watch the Sky! Calendar of Cosmic Events](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/fb--cosmic-events-01.png?1)
2021 Cosmic Calendar
Celestial events and highlights of 2021 and 2022 including supermoons, solar and lunar eclipses, meteor showers, solstices, and equinoxes.
![Full Moon above hill and forest in Slovenia November 15, 2016.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/super-full-moon-november-2016.jpg?1)
What Is a Supermoon?
The Full Moon on May 26, 2021, was a Super Flower Moon. Supermoon, Full Moon—what's the difference?
![Houses and trees in the snow at dusk.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/winter-solstice-nothern-hemisphere.jpg?1)
December Solstice
The December solstice is the summer solstice in the Southern Hemisphere and the winter solstice in the Northern Hemisphere.
![The Sun shining through a naked tree in winter.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/tree-winter-solstice.jpg?1)
When Is Winter Solstice?
The Winter solstice in the Northern Hemisphere is in December, while in the Southern Hemisphere, it's in June.
![New Moon Phase Illustration of the Moon's position in space in relation to Earth and the Sun at New Moon.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/new-moon-phase.png?1)
The New Moon
When is the next New Moon? New Moon is when the Sun and Moon are aligned, with the Sun and Earth on opposite sides of the Moon.
![A tree changing through the four seasons. A tree changing through the four seasons.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/four-seasons-causes.jpg?1)
What Causes Seasons on Earth?
Seasons change because Earth's rotational axis tilts away or towards the Sun during the course of a year.
![September equinox illustration illustration of Earth's position in relation to the Sun's rays at the September equinox](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/september-equinox-dark.png?1)
September Equinox
The Sun shines directly on the Equator on the September equinox and the length of day and night is nearly equal, but not quite.
![Full Moon peeking through branches. Blue and foggy background.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/full-moon-peeking-tree-branches-fog.jpg?1)
What Is a Blue Moon?
'Once in a blue moon', suggests something is very rare. But just how rare is a Blue Moon?
![June solstice illustration Earth's position in relation to the Sun's rays at the June solstice.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/june-solstice-dark.png?1)
June Solstice
The June solstice is the longest day of the year in the Northern Hemisphere & the shortest day in the Southern Hemisphere.
![2 kids watching seagulls at low tide on a beach](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/istock-512273677.jpg?1)
What Causes Tides?
The gravitational pull of the Moon and the Sun makes the water in the oceans bulge, causing a continuous change between high and low tide.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/golden-hour-retriever.jpg?1)
The Golden Hour – When Sunlight Turns Magical
When the Sun is close to the horizon, its light appears warmer and softer. Why is that so? What is the definition of the golden hour? Explanation with photography tips.
![Eclipse History](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/eclipse-traditions.jpg?1)
Solar and Lunar Eclipses
Solar and lunar eclipses, why they occur, when the next eclipse is, and from where you can see them.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/compass-navigation.jpg?1)
Magnetic Declination
A compass needle doesn't point to the geographical North Pole but to magnetic north. Did you know that it usually doesn't point to the magnetic North Pole either?
![March equinox illustration March equinox illustration](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/march-equinox-dark.png?1)
March Equinox
March equinox marks the beginning of spring in the Northern Hemisphere. It is the Southern Hemisphere's autumnal/fall equinox.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/chicago-twilight.jpg?1)
Civil Twilight – Civil Dawn & Dusk
Civil twilight is the brightest of the twilight phases. How is it defined and when does it start and end? What are civil dawn and civil dusk?
![Underside of an airplane visible in front of a half Moon during the day with a blue sky in the background.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/plane-front-of-half-moon.jpg?1)
First Quarter Moon
The 1st Quarter Moon is a primary Moon phase when we can see exactly half of the Moon's surface lit up. Which half depends on where you are on Earth.
![Low angle view of fall forest.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/autumn-leaves-equinox.jpg?1)
When Is Fall Equinox?
The fall (autumnal) equinox in the Northern Hemisphere is in September. In the Southern Hemisphere, it's in March.
![Illustration of a total eclipse of the Sun. Total solar eclipse at its maximum point or totality. (Illustration)](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/total-solar-eclipse.jpg?1)
Total Solar Eclipse
Total solar eclipses occur when the New Moon comes between the Sun and Earth and casts the darkest part of its shadow, the umbra, on Earth.
![A Waxing Gibbous Moon against a black sky. A Waxing Gibbous Moon against a black sky.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/waxing-gibbous-moon.jpg?1)
Waxing Gibbous Moon
The Waxing Gibbous Moon is an intermediate Moon phase that starts after the First Quarter Moon and lasts until the Full Moon.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/aurora.jpg?1)
Northern and Southern Lights
What causes these colorful and dramatic light displays in the sky, and when and from where can you see them?
![Looking up at the Sun framed by buildings.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/city-sun.jpg?1)
What Is Solar Noon?
Noon is at 12 o'clock but solar noon can be at a different time. What's the difference between the two?
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/nautical-twilight-lake.jpg?1)
Nautical Twilight – Nautical Dawn & Dusk
Nautical twilight is the second twilight phase. How is it defined and when does it start and end? What are nautical dawn and nautical dusk?
![Illustrative comparison of a Supermoon and Micromoon.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/supermoon-micromoon.png?1)
What Is Lunar Perigee and Apogee?
Lunar perigee is when the Moon is closest to Earth on its orbit. The point where the Moon is farthest from Earth is known as lunar apogee.
![A Last Quarter Moon is sometimes called a Half Moon. A Last Quarter Moon, also called Half Moon, where the left half of the Moon is lit up.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/third-quarter-moon-half.jpg?1)
Third Quarter Moon
The Third or Last Quarter Moon is when the opposite half of the Moon is illuminated compared to the First Quarter.
![During a total lunar eclipse, the Earth's shadow falls on the Moon, coloring it red. Fully eclipsed Blood Moon.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/lunar-eclipse-shadow.jpg?1)
Total Lunar Eclipses
A total lunar eclipse happens when Earth's shadow blocks the direct light from the Sun reaching the Full Moon.
![A crocus in the spring Sun.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/crocus-spring-equinox.jpg?1)
When Is Spring Equinox?
The Vernal (Spring) Equinox in the Northern Hemisphere is in March. In the Southern Hemisphere, it's in September.
![A sundial casting a shadow.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/sun-dial-time-equation.jpg?1)
Equation of Time
Why doesn't the year's earliest sunset occur on the winter solstice, even though it is the shortest day of the year in terms of daylight?
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/nashville-twilight.jpg?1)
Astronomical Twilight – Astronomical Dawn & Dusk
Astronomical twilight is the darkest of the twilight phases. How is it defined and when does it start and end? What are astronomical dawn and astronomical dusk?
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/waning-gibbous-moon.jpg?1)
Waning Gibbous Moon
The Waning Gibbous Moon is an intermediate Moon phase that starts after the Full Moon and lasts until half of the Moon's face remains lit-up at Third Quarter Moon.
![Sun peeking through trees with snow on the leaves and branches and snow on the ground.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/december-solstice-winter.jpg?1)
December Solstice Facts
10 things you may not know about the December Solstice, the shortest day of the year in the Northern Hemisphere.
![Only a thin crescent of the Sun is visible against a dark sky during this partial solar eclipse Malaysia on 9 March 2016.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/bigstock--123056558.jpg?1)
What Is a Solar Eclipse?
Solar eclipses happen when the Moon moves between Sun and Earth, blocking the Sun's rays and casting a shadow on Earth.
![Sun Distances; Perihelion, Aphelion Diagram showing the distance between the Sun and Earth at different times of the year.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/sun-distances.png?1)
Earth's Perihelion
Earth's closest approach to the Sun is two weeks after the December solstice is a coincidence and has no special significance.
![Sun setting in the background with cloudy sky and trees in the foreground.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/sunset-in-valley.jpg?1)
Equinox: Equal Day & Night?
Equinoxes don't have exactly 12 hours of day and night all over the world, like many believe. Such days, called equilux, do occur, but depend on your location.
![Image of Full Moon red in color due to refraction with dark sky in the background.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/red-full-moon.jpg?1)
Lunar Eclipse: Red Moon
Find out why a totally eclipsed Moon turns a shade of red.
![Astronomy Glossary - Terms & definitions Astronomy Glossary - Terms & definitions](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/fbimage-glossary--astronomy.png?1)
Astronomical Glossary - Terms & Definitions
What do astronomers really mean when they use those technical terms?
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/waxing-crescent-moon.jpg?1)
Waxing Crescent Moon
The Waxing Crescent Moon phase starts after New Moon and lasts until half of the Waxing Moon's surface is illuminated at First Quarter Moon.
![Hindu God Rahu, known for swallowing the sun and causing eclipses. The Hindu deity Rahu.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/hindu-god-rahu.jpg?1)
Solar Eclipse Myths
The solar eclipse has inspired many mythical stories and influenced human behavior. Even today, eclipses of the Sun are considered bad omens in many cultures.
![Dark New Moon night with the star filled sky in the background and fir trees in the foreground.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/starry-night-sky-forest.jpg?1)
What Is a Micromoon?
A Micromoon is the name given to a Full or New Moon when the Moon is farthest from Earth.
![Radio telescopes of the Very Large Array in New Mexico, USA.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/very-large-array.jpg?1)
What Is Universal Time?
Universal Time is a solar time standard used in astronomy and to define time on Earth. How is it measured? What's the difference between UT, UT0, UT1, UT2, and UTC?
![Star trails over an observatory. Star trails over an observatory.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/star-trails-length-day.jpg?1)
How Long Is a Day on Earth?
In terms of solar time, most days are a little longer than 24 hours. Exact day length for today and yesterday.
![Illustration showing Earth's axis drawn as a red line.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/axial-tilt.png?1)
Earth Is Tilted
When an object the size of Mars crashed into the newly formed planet Earth around 4.5 billion years ago, it knocked it over and left it tilted at an angle.
![Dark New Moon night with the star filled sky in the background and fir trees in the foreground.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/starry-night-sky-forest.jpg?1)
What Is a Black Moon?
A Black Moon can be the third New Moon in a season with four New Moons or the second New Moon in the same calendar month, or even no New Moon at all.
![The Sun shining through the Stonehenge ancient monument.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/stonehenge-solstice2.jpg?1)
When Is Summer Solstice?
The summer solstice in the Northern Hemisphere is in June, while in the Southern Hemisphere, it's in December.
![Black background with rays extending out from a circle and a bright light from the top of the circle.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/totality-great-american-total-solar-eclipse.jpg?1)
How Often Do Solar Eclipses Happen?
There are between 2 and 5 solar eclipses every year, each one visible only in a limited area.
![A close-up of the thin sliver of a yellow waning crescent moon.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/waning-crescent-moon-yellow.jpg?1)
Waning Crescent Moon
During the Waning Crescent Moon phase, the lit-up part of the Waning Moon shrinks from the Third Quarter Moon until it disappears from view at New Moon.
![A sundial with the Sun casting a shadow. A sundial with the Sun casting a shadow.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/sundial-local-mean-time.jpg?1)
What Is Local Mean Time?
Use a sundial to determine the time of day and you will probably be off by a few minutes. That's where LMT comes into play. How is it measured and what is it used for?
![Dark blue sky in the background with a glowing ring around the Sun. The center of the sun is dark.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/annular-eclipse-new-mexico-2012.jpg?1)
Annular Solar Eclipse
An annular solar eclipse is when the Moon moves in front of the Sun but leaves the outer edge of the Sun visible as a ring of fire.
![Image of a waterfall at night with one bright moon bow and a faint moon bow above it. Dark skies and city lights in the background.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/double-moonbow-over-yosemite.jpg?1)
What Are Moonbows?
Moonbows occur when the Moon’s light is reflected and refracted off water droplets in the air.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/total-solar-eclipse-com.png?1)
What Is the Umbra?
The umbra is the dark center portion of a shadow. The Moon's umbra causes total solar eclipses, and the Earth's umbra is involved in total and partial lunar eclipses.
![Meteor showers are easy to view. All you need is some patience, a dark viewing spot, and our Interactive Meteor Shower Sky Map. A man's silhouette with the milky way and a meteor in the backdrop.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/viewing-meteor-shower.jpg?1)
Meteors: How to See
Dates and tips on how and where to see shooting stars from meteor showers all over the world.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/dusk-kyoto.jpg?1)
What Is Dusk?
Dusk generally refers to the transition from sunset to nighttime, and the term is often used as another word for evening twilight. However, science defines dusk on the basis of the angle that the Sun makes with the horizon.
![Image of a faint eclipsed Moon behind a brightly it castle.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/lunar-eclipse-siena.jpg?1)
Watching Lunar Eclipses
A lunar eclipse can be seen with the naked eye, unlike solar eclipses, which have special safety requirements.
![Picture with fields in the foreground and a crescent shaped Sun with Moon in front of it. Cloudy skies in the background.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/partial-solar-eclipse-arkansas.jpg?1)
Partial Solar Eclipse
A partial solar eclipse happens when the Moon only partially covers the Sun.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/santorini-dawn.jpg?1)
What Is Dawn?
Dawn generally refers to the transition from night to day as the morning twilight brightens the sky. However, there is also a formal definition that refers to specific moments during that transition.
![Illustration of altitude and azimuth in the celestial sphere.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/horizontal-coordinate-system.png?1)
Altitude & Azimuth: The Horizontal Coordinate System
Learn how to use altitude (elevation) and azimuth angles to locate any object in the sky, such as stars, planets, satellites, the Sun, or the Moon.
![A pathway in a park during fall (autumn). A pathway in a park during fall (autumn).](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/september-equinox-facts.jpg?1)
10 September Equinox Facts
10 things you may not know about the September Equinox.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/tell-time-with-stars.png?1)
Timekeeping by Stars
Out and about at night without a watch or a smartphone readily available? If you are in the Northern Hemisphere use the Big Dipper and the North Star to tell the time.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/shadow-experiments-antumbra.png?1)
Why 3 Shadows?
Objects cast 3 different shadows: umbra, penumbra, and antumbra. Why are there 3 types of shadows and how do they determine the type of an eclipse?
![The full moon can look larger on the horizon than when higher up in the sky. Full moon on the horizon at the end of a dock.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/moon-illusion.jpg?1)
The Moon Illusion
Some days, the Full Moon at the horizon looks larger than a normal Full Moon. Does the Moon really change size or is this an illusion?
![Illustration showing all the different Moon phases next to one another](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/moon-phases-together.jpg?1)
The Lunar Month
A lunar month is the time it takes the Moon to pass through all of the Moon phases, usually measured from a New Moon the next New Moon.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/asteroid-10-things.jpg?1)
What are Asteroids?
Learn more about these space rocks orbiting the Sun.
![Eclipse History](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/eclipse-traditions1.jpg?1)
Solar Eclipses in History
Solar eclipses were historically seen as omens that bring about death and destruction. People in many ancient civilizations tried their best to understand them.
![The village of Mararola, Italy, during the blue hour.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/blue-hour-cinque-terre.jpg?1)
The Blue Hour
The blue hour in the morning and evening is a favorite with photographers. How is it defined? When does it start & end? Explanation with times, degrees & photography tips.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/sunhalo.jpg?1)
Halos, Sundogs and Light Pillars
These are atmospheric phenomena created by the reflection and refraction of light by ice crystals in the atmosphere.
![A partially eclipsed Moon in the night sky. A little over half of the Moon is covered by a reddish shade.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/partial-lunar-eclipse-cropped.jpg?1)
What Is a Partial Lunar Eclipse?
A partial lunar eclipse happens when the Earth moves between the Sun and the Moon, but they are not precisely aligned.
![Lunar Eclipse Penumbral Penumbral lunar eclipse illustration with positions of Sun, Earth, and Moon in space](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/totallunareclipsepenumbral.png?1)
What Is the Penumbra?
The penumbra is the lighter outer part of a shadow. The Moon's penumbra causes partial solar eclipses, and the Earth's penumbra is involved in penumbral lunar eclipses.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/mercury-transit.png?1)
Mercury Transit
When Mercury transits the Sun, you can see it as a tiny black dot silhouetted against the Sun's disk. The last Mercury transit was on November 11, 2019.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/measuring-sky-with-hand.png?1)
How to measure the sky
Measure the sky and find out distances between celestial objects using your hands and fingers.
![Sun peeking through trees with snow on the leaves and branches and snow on the ground.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/december-solstice-winter.jpg?1)
December Solstice Customs
Learn more about the customs, traditions and events surrounding the December solstice.
![Nordlys over en nordnorsk fjord i mørketiden. Nordlys over en nordnorsk fjord i mørketiden.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/nordlys-morketid.jpg?1)
What Are Polar Nights?
A Polar Night is a night that lasts for at least 24 hours. It's the opposite of Midnight Sun / Polar Day.
![Viewing eclipse with a DIY pinhole projector Diagram of a DIY pinhole projector.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/pinhole-projector-diy.png?1)
Make a Pinhole Projector
Make a simple pinhole projector using 2 pieces of card or paper to safely watch a projection of a solar eclipse.
![A comet glowing in the dark winter sky.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/178087321.jpg?1)
What Are Comets?
Comets are small celestial bodies that orbit the Sun. Primarily made of dust and ice, many have a tail (coma) and are thought to be remnants of the formation of the Solar System.
![Annular solar eclipse illustration with positions of Earth, Moon, and Sun in space](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/annular-solar-eclipse.png?1)
What Is the Antumbra?
The antumbra is the lighter part of a shadow that forms at a certain distance from the object casting the shadow. It is involved in annular solar eclipses and planet transits.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/tropical-year-illustration.png?1)
A Year Is Never 365 Days
The definition of a tropical year is the time it takes the Earth to complete a full orbit around the Sun. It is approximately 365.242189 days long.
![A Full Moon against a dark sky.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/full-moon-dark-eclipse.jpg?1)
Penumbral Lunar Eclipse
A penumbral lunar eclipse occurs when the outer shadow of Earth falls on the Moon's face. It is easy to miss this type of lunar eclipse.
![Parents playing with their young daughter in the evening sun](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/evening-family.jpg?1)
June Solstice Facts
11 things you may not know about the June Solstice.
![Position of Sun, Moon, and Earth during a hybrid solar eclipse.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/hybrid-solar-eclipse.png?1)
Hybrid Solar Eclipse
A hybrid eclipse or annular/total eclipse starts as a total solar eclipse but changes into an annular solar eclipse. Why is that so? When is the next hybrid solar eclipse?
![Illustration of a solar analemma figure-of-eight above a city skyline](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/solar-analemma-ill.jpg?1)
Solar Analemma
A Solar Analemma is a graph showing the position of the Sun in the sky above a single location at the same time of the day throughout the course of a year.
![The morning and evening sky can turn different shades of red and orange because of Rayleigh Scattering. Colorful morning sky over Barcelona](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/barcelona-morning-sky.jpg?1)
Rayleigh Scattering
Why does the sky turn red during sunrise and sunset?
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/magnitude-of-eclipse.png?1)
Eclipse Magnitude
Eclipse magnitude is a number that astronomers associate with solar or lunar eclipses. What does it mean?
![Illustration of eclipse glasses, binoculars and telescope with eclipse safe lens with a green check mark next to them.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/how-to-view-a-solar-eclipse-do-02.png?1)
Safely See a Solar Eclipse
Protect your eyes during a solar eclipse. Sunglasses don't work.
![Close-up of the far side of the Moon with partial Earth in the background.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/far-side-moon-image-nasa.jpg?1)
The Moon's Far Side
The notion that there is a permanently dark side of the Moon is wrong. What is true, is that there is a far side of the Moon, a side we never see from Earth
![Snowdrops growing up trough the snow.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/snowdrops-snow-spring.jpg?1)
March Equinox Facts
On Sat, March 20, 2022, day and night will be of almost equal duration in most time zones in the world.
![Diagram of a box pinhole projector.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/pinhole-projector-homemade.png?1)
Make a Box Pinhole Projector
Instructions on how to DIY a pinhole projector using a cardboard box and household items to safely see a solar eclipse.
![Diagram of a DIY projector with binoculars.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/pinhole-projector-binoculors.png?1)
Make a Solar Eclipse Projector
Make a Sun projector a pair of binoculars or a telescope to safely watch solar eclipses or a planet transit.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/stonehenge-june-solstice.jpg?1)
June Solstice Traditions
In many Northern Hemisphere cultures, the June solstice is associated with holidays, feasts and celebrations.
![Crescent Moon with dark blue sky in the background. The unlit part of the Moon has a dim glow. Bright star shines to the left of the Moon.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/earthshine.jpg?1)
What Is Earthshine?
Earthshine is a dull glow that occurs when the Sun’s light reflects off the Earth's surface and illuminates the unlit portion of the Moon.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/venus-transit.jpg?1)
Transit of Venus: June 5-6, 2012
The 2012 Venus transit was the last chance to see this phenomenon for over 100 years. Mercury transits happen more often, the next one in 2032.
![A partially red Moon rising from behind mountains.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/blood-moon-mountain.jpg?2)
Lunar Eclipse Photography
Planning to take pictures of a lunar eclipse? Follow our guide for amazing eclipse photos! We tell you what kind of equipment you need and how to use it.
![Meteors are nature's fireworks. Meteors from Perseids meteor shower, 2017 behind the Milky Way observatory, Calgary, Canada.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/meteor-showers-milky-way-observatory.jpg?1)
What Is a Meteor Shower
Dates and tips on how and where to see "shooting stars" from meteor showers all over the world.
![Starry night sky in the background with desert in the foreground. White truck on the side and a triangular glow of zodiacal lights in the sky.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/starry-night-zodiacal-lights-morocco-desert.jpg?1)
Zodiacal lights
Also known as false dawn, zodiacal lights are rare optical phenomena that occur around sunset and sunrise in early spring and late fall.
![Eclipse glasses held up towards a solar eclipse.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/iphone-eclipse-photo-2.jpg?1)
Solar Eclipse Photography
Take that perfect solar eclipse photo with your camera and some extra equipment, or capture it with your mobile phone.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/tropical-year-lengths.png?1)
Length of Tropical Years 1900–2100
Exact length down to the second of tropical years ranging from 1900 to 2100. It is also known as a solar year, astronomical year, or equinoctial year.
![Close-up image of the Full Moon.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/not-blue-moon.jpg?1)
Is a Blue Moon Blue?
A Blue Moon is a type of a Full Moon. It can also be a rare Moon that looks blue due to atmospheric dust particles.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/lovejoy.jpg?1)
All about Comet Lovejoy
Comet Lovejoy (C/2013 R1) is one of 3 comets that will grace the skies in November, 2013.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/mars-venus-jupiter-27oct.png?1)
Jupiter and Venus Closest Conjunction of 2015
From time to time, some of the planets in our solar system are in conjunction and become visible together in the sky. Venus, Jupiter, Mars, and Mercury have all been visible in the early mornings of October 2015.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/ison.jpg?1)
All about Comet ISON
Everything you need to know about Comet ISON or C/2012 S1.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/asteroid-2004bl86.jpg?1)
Asteroid 2004 BL86 to Fly By Earth
On Monday, January 26, 2015 asteroid 2004 BL86 flew by at only 3 times the distance of the Moon from the Earth. It will be the largest celestial body to come this close to Earth until 2027.
![Illustration image](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/comet.jpg?1)
2013: Year of comets
2013 is going to be a good year for comet watchers, with at least 3 comets that may be visible without the aid of sophisticated equipment.
![An image of the solar system showing the alignment of the Earth, Jupiter, and Saturn for the Great Conjunction of 2020.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/great-conjunction-2020.png?1)
What Is a Conjunction?
A conjunction is when planets like Mars, Jupiter, or Saturn, or other bodies like stars or the Moon, meet in the sky. Why and when do conjunctions happen?
![A happy couple running through the waves on a sunlit beach.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/sunset-photography.jpg?1)
Sunrise and Sunset Photography
Use your smartphone to take impressive pictures during sunrise and sunset.
![Silhouette of two photographers looking at the Full Moon.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/moon-photography-camera.jpg?1)
Taking Pictures of the Moon
With the right equipment, a little time and planning, you can take great pictures of the Moon.
![Illustration showing the Moon phases based on Moon images from NASA.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/lunar-cycle.jpg?1)
The Moon Phases
There are four primary Moon phases and four intermediate phases. New Moon First Quarter Full Moon Third or Last Quarter Waxing and Waning Crescent Moon.
![See 46P/Wirtanen zoom across the sky with the Night Sky Map. Screenshot of the Night Sky Map showing Comet Wirtanen's path.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/comet-46p-wirtanen-night-sky-map.png?1)
Brightest Comet of 2018
Comet 46P/Wirtanen will grace the night sky in December 2018. Find when, how, and where to see the brightest comet of the year with your naked eyes.
![Comet in the dark sky over a mountain with a setting/rising Sun in the background.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/neowise-above-mountain-slovakia.jpg?1)
Brightest Comet of 2020
Comet C/2020 F3 NEOWISE will grace the night sky in July 2020. Find when, how, and where to see the brightest comet of the year with your naked eyes.
![Screenshot of timeanddate.com's Night Sky Map for December 21, 2020, shortly after sunset in the northern hemisphere.](http://webcf.waybackmachine.org/web/20210812180448im_/https://c.tadst.com/gfx/150x84/night-sky-map-great-conjunction.jpg?1)
Great Conjunction 2020
In December 2020, Jupiter and Saturn met in the sky in a rare Great Conjunction.