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FAQs

What is the blue hour?

Blue hour by Marianna Bucina Roca in Gloucester, Massachusetts.

Blue hour by Marianna Bucina Roca in Gloucester, Massachusetts.

When you see a strong blue tone to photographs, it could be that the photographer has taken advantage of the blue hour. That’s a time of day when the sun has just set or is about to rise, when the sky overhead takes on a deep blue color, and when the landscape is suffused with bluish light. The blue hour is a good time to take photos of the moon, because then the moon’s glare isn’t so bright in contrast to the sky. It’s also a good time to take landscape photos, as the photos in this post show.

How to see a green flash

San Diego, California on October 25, 2012, taken by EarthSky Facebook friend Jim Grant.  Thanks Jim!

San Diego, California on October 25, 2012, taken by EarthSky Facebook friend Jim Grant. Thanks Jim!

It’s said that once you’ve seen a green flash, you’ll never go wrong in matters of the heart. Here’s all you need to know to see the legendary green flash, plus great pics.

What makes a red rainbow?

Göran Strand of Sweden captured this double red rainbow.  Used with permission.

Photo by Göran Strand. Used with permission.

Astrophotographer Göran Strand of Sweden kindly gave us permission to publish this photo, which a phenomenal double red rainbow. Details … inside.

How often do 7 eclipses occur in 365 days?

Annular eclipse image credit: Wikipedia

Annular eclipse image credit: Wikipedia

The last time seven eclipses occurred in a period of one year was from November 13, 2012, to November 3, 2013. It will next happen in the time period from January 31, 2018, to January 21, 2019.

Video: Why does the moon look so big on the horizon?

The August 10 supermoon might look super big seen near a horizon. But all full moons look big near a horizon, due to an illusion called the moon illusion.

What is a supermoon?

What most call a Blue Moon isn't blue in color. It's only Blue in name. This great moon photo from EarthSky Facebook friend Rebecca Lacey in Cambridge, Idaho.

What does a full supermoon look like? Astronomers say you can’t really detect any difference with your eye between a supermoon and any ordinary full moon. This great moon photo is from Rebecca Lacey in Cambridge, Idaho.

It’s supermoon Sunday! We in astronomy used to call them perigean new moons or perigean full moons, that is, new or full moons closely coinciding with perigee – the moon’s closest point to Earth in its orbit. But, like almost everyone else, now we enjoy calling them supermoons. The name supermoon was coined by an astrologer, Richard Nolle, over 30 years ago. It was popularized and came to be the accepted term for most people only in the past few years. Are supermoons hype? In our opinion … gosh, no, just modern folklore. And they can cause real physical effects, such as larger-than-usual tides. The year 2014 has a total of five supermoons. They are the two new moons of January, and the full moons of July, August and September. It’Follow the links inside to learn about the supermoons of 2014.

What’s the birthstone for August?

Peridot

Peridot

Happy birthday to our August friends! This is one of your birthstones, peridot. Your other birthstone is sardonyx.

Read about both your birthstones….

How to see anticrepuscular rays

View larger. | Anticrepuscular rays - seen in the east at sunset - in Nevada.  Shreenivasan Manievannan posted this photo on EarthSky Facebook in July 2014.  Visit Shreeniclix Photography.

Anticrepuscular rays – seen in the east at sunset – in Nevada. Shreenivasan Manievannan posted this photo on EarthSky Facebook in July 2014.

Next time you see crepuscular rays or sunrays extending from the horizon … turn around. You might catch a glimpse of elusive anticrepuscular rays.

Can sharks smile? Do they even feel happy?

The Discovery Channel’s Shark Week is coming up (starts August 10) and sharks are on our mind ….

Attributing emotions to animals is almost irresistible to most people, and some animals do seem to show happiness, anger, fear, and other feelings. Dogs, cats, dolphins, and monkeys can be especially expressive. So … how about sharks?

Will the Andromeda galaxy someday collide with our Milky Way?

Image Credit: NASA, ESA et al.

This image represents Earth’s night sky in 3.75 billion years. The Andromeda galaxy (left) will fill our field of view then, astronomers say, as it heads toward a collision with our Milky way galaxy. Image Credit: NASA, ESA et al.

It’s a question people ask us… Will our home galaxy someday collide with the next-nearest spiral galaxy, in the direction of the constellation Andromeda? And if so, when?