Moon in front of Cancer on February 27

On February 27, 2018, the almost-full waxing gibbous moon puts the constellation Cancer in the spotlight, but out of view. Demure Cancer the Crab is the faintest of the 13 constellations of the zodiac. You can see Cancer only on dark, moonless nights.

The starry sky is like a great big connect-the-dots book, enabling stargazers to star-hop from brighter stars to more obscure nighttime treasures. And that’s why noticing the stars around the February 27, 2018, moon can be helpful. By around the end of the first week of March, when the moon drops out of the evening sky, Cancer the Crab will be showing its delicate starlit figurine in the region of sky in between the Leo star Regulus and the Gemini stars Castor and Pollux.

Identify Regulus, Castor and Pollux now, and you can use them for years to come to help you identify Cancer.

Our featured chart at top shows the moon and Cancer for North American mid-northern latitudes. At nightfall, at mid-northern latitudes from around the world, the stars and planets are similarly positioned. As seen from Europe and Asia, though, the moon on February 27, 2018, is offset toward the Gemini stars, Castor and Pollux. This difference in the moon’s position, relative to the backdrop stars of the zodiac, is due to the moon’s own motion in orbit around Earth.

The constellation Cancer via the International Astronomical Union (IAU). On a dark night, look for the Beehive star cluster (M44) to make a triangle with the Gemini stars, Castor and Pollux, and the bright star Procyon.

From the Southern Hemisphere, the differences are due in part to the moon’s movement, and in part to the difference in perspective from one hemisphere to the other. Still, we all live under the same sky, and no matter where you live worldwide, the moon beams in the vicinity of Cancer tonight, with the moon sandwiched in between Castor and Pollux on one side and the star Regulus on the other.

Just remember – although we outline Cancer for you on our chart, you’re not likely to see this constellation in the drenching moonlight on February 27. Notice the stars around it, and come back in 10 days so to find the faint Crab when the moon has moved on its way – and left the evening sky dark for stargazing.

Bottom line: The almost-full moon puts the constellation Cancer the Crab in the spotlight – but out of view – on the night of February 27, 2018.

Cancer? Here’s your constellation

Beehive cluster: 1,000 stars in Cancer

from EarthSky http://ift.tt/1KxlIpG

On February 27, 2018, the almost-full waxing gibbous moon puts the constellation Cancer in the spotlight, but out of view. Demure Cancer the Crab is the faintest of the 13 constellations of the zodiac. You can see Cancer only on dark, moonless nights.

The starry sky is like a great big connect-the-dots book, enabling stargazers to star-hop from brighter stars to more obscure nighttime treasures. And that’s why noticing the stars around the February 27, 2018, moon can be helpful. By around the end of the first week of March, when the moon drops out of the evening sky, Cancer the Crab will be showing its delicate starlit figurine in the region of sky in between the Leo star Regulus and the Gemini stars Castor and Pollux.

Identify Regulus, Castor and Pollux now, and you can use them for years to come to help you identify Cancer.

Our featured chart at top shows the moon and Cancer for North American mid-northern latitudes. At nightfall, at mid-northern latitudes from around the world, the stars and planets are similarly positioned. As seen from Europe and Asia, though, the moon on February 27, 2018, is offset toward the Gemini stars, Castor and Pollux. This difference in the moon’s position, relative to the backdrop stars of the zodiac, is due to the moon’s own motion in orbit around Earth.

The constellation Cancer via the International Astronomical Union (IAU). On a dark night, look for the Beehive star cluster (M44) to make a triangle with the Gemini stars, Castor and Pollux, and the bright star Procyon.

From the Southern Hemisphere, the differences are due in part to the moon’s movement, and in part to the difference in perspective from one hemisphere to the other. Still, we all live under the same sky, and no matter where you live worldwide, the moon beams in the vicinity of Cancer tonight, with the moon sandwiched in between Castor and Pollux on one side and the star Regulus on the other.

Just remember – although we outline Cancer for you on our chart, you’re not likely to see this constellation in the drenching moonlight on February 27. Notice the stars around it, and come back in 10 days so to find the faint Crab when the moon has moved on its way – and left the evening sky dark for stargazing.

Bottom line: The almost-full moon puts the constellation Cancer the Crab in the spotlight – but out of view – on the night of February 27, 2018.

Cancer? Here’s your constellation

Beehive cluster: 1,000 stars in Cancer

from EarthSky http://ift.tt/1KxlIpG

Where’s the moon? Waxing gibbous

February 26, 2018 waxing gibbous moon via Mohamed Laaifat Photographies in Normandy, France.

The moon is now in a waxing gibbous phase, rising between noon and sunset, setting in the wee hours after midnight. You’ll always see a waxing gibbous moon between a first quarter moon and full moon, and, it so happens, the upcoming full moon – on the night of March 1, 2018 is the first of two full moons for the month of March. The second full moon – coming up on March 31, 2018 – will be called by the name Blue Moon.

Any moon that appears more than half lighted but less than full is called a gibbous moon. The word gibbous comes from a root word that means hump-backed.

People often see a waxing gibbous moon in the afternoon, shortly after moonrise, while it’s ascending in the east as the sun is descending in the west. It’s easy to see a waxing gibbous moon in the daytime because, at this phase of the moon, a respectably large fraction of the moon’s dayside is now facing our way.

Read more: 4 keys to understanding moon phases.

Read more about Blue Moons

Point of interest on a waxing gibbous moon: Sinus Iridum (Bay of Rainbows) surrounded by the Jura Mountains. Photo by Lunar 101-Moon Book in Toronto, Canada.

As the moon orbits Earth, it changes phase in an orderly way. Follow these links to understand the various phases of the moon.

Four keys to understanding moon phases

Where’s the moon? Waxing crescent
Where’s the moon? First quarter
Where’s the moon? Waxing gibbous
What’s special about a full moon?
Where’s the moon? Waning gibbous
Where’s the moon? Last quarter
Where’s the moon? Waning crescent
Where’s the moon? New phase

from EarthSky http://ift.tt/1j8UWzb

February 26, 2018 waxing gibbous moon via Mohamed Laaifat Photographies in Normandy, France.

The moon is now in a waxing gibbous phase, rising between noon and sunset, setting in the wee hours after midnight. You’ll always see a waxing gibbous moon between a first quarter moon and full moon, and, it so happens, the upcoming full moon – on the night of March 1, 2018 is the first of two full moons for the month of March. The second full moon – coming up on March 31, 2018 – will be called by the name Blue Moon.

Any moon that appears more than half lighted but less than full is called a gibbous moon. The word gibbous comes from a root word that means hump-backed.

People often see a waxing gibbous moon in the afternoon, shortly after moonrise, while it’s ascending in the east as the sun is descending in the west. It’s easy to see a waxing gibbous moon in the daytime because, at this phase of the moon, a respectably large fraction of the moon’s dayside is now facing our way.

Read more: 4 keys to understanding moon phases.

Read more about Blue Moons

Point of interest on a waxing gibbous moon: Sinus Iridum (Bay of Rainbows) surrounded by the Jura Mountains. Photo by Lunar 101-Moon Book in Toronto, Canada.

As the moon orbits Earth, it changes phase in an orderly way. Follow these links to understand the various phases of the moon.

Four keys to understanding moon phases

Where’s the moon? Waxing crescent
Where’s the moon? First quarter
Where’s the moon? Waxing gibbous
What’s special about a full moon?
Where’s the moon? Waning gibbous
Where’s the moon? Last quarter
Where’s the moon? Waning crescent
Where’s the moon? New phase

from EarthSky http://ift.tt/1j8UWzb

Ecosystems hanging by a thread

Emory disease ecologist Thomas Gillespie served on an international committee that developed best practice guidelines for health monitoring and disease control in great ape populations, part of a growing public education effort.

By Tony Rehagen
Emory Magazine

Thomas Gillespie’s parents and teachers always wanted him to go into medicine.

“Growing up in Rockford, Illinois, if you were smart and interested in biology, you were supposed to be a doctor,” he says.

Gillespie, meanwhile, was always more interested in primates. In seventh grade, he phoned animal psychologist Penny Patterson, famous for teaching the gorilla Koko how to use sign language, and interviewed the scientist about Koko’s diet while punching out notes on a typewriter. He was premed at the University of Illinois, but spent his internship at the Brookfield Zoo in Chicago, working in the “Tropic World” primate exhibit. His favorite undergrad course was biological anthropology, the study of biological and behavioral aspects of humans and nonhuman primates, looking at our closest relatives to better understand ourselves.

Gillespie eventually took a year off before graduate school to work with primate communities in the Peruvian Amazon. The apes finally won out — Gillespie would choose a doctorate in zoology over medical school.

But it wasn’t long before the two fields of study collided. While monitoring the group behavior of colobine monkeys in Africa, Gillespie observed that some of the animals were eating bark from the African cherry tree — not a typical food source for them. When he dug deeper, Gillespie learned that human doctors in the region used that same bark to treat parasites in their patients. The monkeys, he realized, were self-medicating.

“That discovery in these monkeys brought me back toward the health science side of biology,” says Gillespie.

Gillespie’s return to a medical approach to zoology came not a moment too soon—for the sake of the primates and maybe even all of humankind. As an associate professor in Emory’s Department of Environmental Sciences specializing in the disease ecology of primates, Gillespie and his team of researchers have helped uncover a crisis among our nearest taxonomic neighbors. According to an article coauthored by Gillespie and thirty other experts and published in the journal Science Advances, 75 percent of the world’s five-hundred-plus primate species are declining in population, and a whopping 60 percent face extinction, largely due to human encroachment.

Read more in Emory Magazine.

Related:
Experts warn of impending extinction of many of the world's primates
Chimpanzee studies highlight disease risks to all endangered wildlife

from eScienceCommons http://ift.tt/2EZhS7i

Emory disease ecologist Thomas Gillespie served on an international committee that developed best practice guidelines for health monitoring and disease control in great ape populations, part of a growing public education effort.

By Tony Rehagen
Emory Magazine

Thomas Gillespie’s parents and teachers always wanted him to go into medicine.

“Growing up in Rockford, Illinois, if you were smart and interested in biology, you were supposed to be a doctor,” he says.

Gillespie, meanwhile, was always more interested in primates. In seventh grade, he phoned animal psychologist Penny Patterson, famous for teaching the gorilla Koko how to use sign language, and interviewed the scientist about Koko’s diet while punching out notes on a typewriter. He was premed at the University of Illinois, but spent his internship at the Brookfield Zoo in Chicago, working in the “Tropic World” primate exhibit. His favorite undergrad course was biological anthropology, the study of biological and behavioral aspects of humans and nonhuman primates, looking at our closest relatives to better understand ourselves.

Gillespie eventually took a year off before graduate school to work with primate communities in the Peruvian Amazon. The apes finally won out — Gillespie would choose a doctorate in zoology over medical school.

But it wasn’t long before the two fields of study collided. While monitoring the group behavior of colobine monkeys in Africa, Gillespie observed that some of the animals were eating bark from the African cherry tree — not a typical food source for them. When he dug deeper, Gillespie learned that human doctors in the region used that same bark to treat parasites in their patients. The monkeys, he realized, were self-medicating.

“That discovery in these monkeys brought me back toward the health science side of biology,” says Gillespie.

Gillespie’s return to a medical approach to zoology came not a moment too soon—for the sake of the primates and maybe even all of humankind. As an associate professor in Emory’s Department of Environmental Sciences specializing in the disease ecology of primates, Gillespie and his team of researchers have helped uncover a crisis among our nearest taxonomic neighbors. According to an article coauthored by Gillespie and thirty other experts and published in the journal Science Advances, 75 percent of the world’s five-hundred-plus primate species are declining in population, and a whopping 60 percent face extinction, largely due to human encroachment.

Read more in Emory Magazine.

Related:
Experts warn of impending extinction of many of the world's primates
Chimpanzee studies highlight disease risks to all endangered wildlife

from eScienceCommons http://ift.tt/2EZhS7i

Does losing weight reduce the risk of cancer?

Obesity is the biggest cause of cancer in the UK, after smoking.

But this isn’t well known.

When people do hear this, we’re often asked: ‘I’m already overweight, will losing weight reduce my risk?’

And with 2 in 3 UK adults either overweight or obese, it’s an important question. But while it sounds logical that losing weight would reduce the risk, proving this isn’t easy.

When studying people, separating those who lose weight intentionally from those who lose it because they’re already ill can be tough. On top of that, losing weight and keeping it off is hard.

But this hasn’t stopped researchers from hunting for answers. And the good news is, research so far tells us that weight loss is beneficial when it comes to reducing cancer risk.

Understanding weight gain

Years of research have shown that the more weight gained, the higher the risk of cancer.

Most of this evidence comes from studies that have used body mass index (BMI) as a measure of body fat.

But BMI can only provide a snapshot of someone’s weight.

Other studies have looked at how long someone is overweight. And the results suggest that the longer someone is overweight, the higher their risk

Based on this, losing weight (and keeping it off) means you stop accumulating more risk, and reduce your risk compared to what it would be if you gained more weight. So losing weight does help, both with cancer risk and your general health.

But this doesn’t fully answer our question: can an increased risk go back down to the level it would have been had the extra weight never been there?

Weight loss through surgery

One of the most effective, although extreme, ways for people who are very overweight to lose weight is bariatric surgery. This covers a range of surgical techniques, such as stomach stapling or surgically bypassing large parts of the gut.

Because people lose a lot of weight after surgery, and keep most of it off, it’s more likely researchers will find an effect on cancer risk if it’s there.

It’s also more likely any effect would be due to weight loss itself, rather than lifestyle changes that reduce cancer risk. These studies also help untangle the effects of losing weight intentionally and weight loss due to illness.

Results from studies post-surgery are mixed, but overall they suggest that people who undergo bariatric surgery do have a reduced risk of cancer compared to those who don’t.

The strongest evidence so far is for women, but evidence is growing in men too.

A study that combined the results of 6 others found a staggering 45% reduction in cancer risk among formerly obese people who had bariatric surgery. But when they split the results by gender, this finding only remained in women.

A more recent US study, which included over 2500 cancer cases, also found a reduction in cancer risk in people who had surgery based on 3.5 years of follow up. And the reduced risk was seen for a range of cancers, including breast, colon, pancreatic and womb.

So the results so far are promising, and suggest weight loss can reverse increased cancer risk.

But there are limitations. Firstly, major surgery isn’t the solution for everyone. And it’s possible that people who have surgery differ in ways these studies don’t account for. And weight loss through surgery could have different effects to weight loss by other means.

Weight loss outside the operating room

A 2012 review looked at 6 weight loss studies and 5 of these linked intentional weight loss with a reduced risk of cancer.

But a more recent study, looking at the results of weight loss trials (mostly low-fat diets), didn’t find they reduced cancer risk. But the quality of evidence for cancer was rated as very low – overall the original trials only included a small number of cancer cases (103 in total) and the average amount of weight lost after 3 years was small.

These findings illustrate how difficult it is to study weight loss in the real world. So the evidence isn’t as strong. But what’s there is promising, although as with surgery studies the strongest evidence is for women – specifically for breast cancer.

How might weight loss help?

A rigorous 2016 review of how extra fat affects the body found good evidence that intentional weight loss affects key ways obesity is thought to cause cancer: namely hormones and inflammation.

And studies since have also found this.

But we don’t yet fully understand all the ways obesity causes cancer. So there’s still more to know about how weight loss could reverse these effects.

Why is there seemingly more of an effect in women?

There are many possible explanations. It could be that because these female cancers are common, there are more cases to study. This increases the chance of finding an effect if it’s there.

But it’s also possible that cancers strongly linked to sex hormones, such as womb and breast, are more quickly affected by weight loss, whereas for other cancers it may take longer to see an effect. For example, weight loss can quickly reduce levels of oestrogen in the body, and high levels of oestrogen are almost certainly how obesity causes womb and breast cancer.

Cancers more common in men, such as bowel cancer, may take longer to see an effect. This might explain why this study showed no impact of weight loss on bowel cancer risk after 7 years of follow up. This study also couldn’t distinguish between intentional and unintentional weight loss.

What’s likely is that weight loss affects different parts of the body in different ways, and this is reflected in how it might affect cancer risk. This makes sense, as weight gain affects cancer risk differently for different cancers. Studies in the future will need to take this into account.

Prevention is still best, but weight loss is worth it

So, the answer to our original question – does losing weight reduce cancer risk? – seems to be: yes.

If you are overweight, you can reduce your risk by avoiding gaining more weight.

And overall, all the research carried out so far suggests that an increased risk can start to fall with weight loss.

Plus, the best way to lose weight for most people is by eating and drinking healthily and moving more, all of which can reduce the risk of cancer independently.

But the fact remains that losing weight and keeping it off can be incredibly hard. So this must be supported by public health measures (like the sugary drinks tax) that make healthy choices easy for everyone, both to prevent weight gain, and to help those lose it who need to.

Never gaining extra weight in the first place is still best for reducing cancer risk. But we know that’s not possible for everyone – and it doesn’t help people who have already gained weight. So having evidence that weight loss could help is good news.

Emma Shields is a senior health information officer at Cancer Research UK

from Cancer Research UK – Science blog http://ift.tt/2ESxde3

Obesity is the biggest cause of cancer in the UK, after smoking.

But this isn’t well known.

When people do hear this, we’re often asked: ‘I’m already overweight, will losing weight reduce my risk?’

And with 2 in 3 UK adults either overweight or obese, it’s an important question. But while it sounds logical that losing weight would reduce the risk, proving this isn’t easy.

When studying people, separating those who lose weight intentionally from those who lose it because they’re already ill can be tough. On top of that, losing weight and keeping it off is hard.

But this hasn’t stopped researchers from hunting for answers. And the good news is, research so far tells us that weight loss is beneficial when it comes to reducing cancer risk.

Understanding weight gain

Years of research have shown that the more weight gained, the higher the risk of cancer.

Most of this evidence comes from studies that have used body mass index (BMI) as a measure of body fat.

But BMI can only provide a snapshot of someone’s weight.

Other studies have looked at how long someone is overweight. And the results suggest that the longer someone is overweight, the higher their risk

Based on this, losing weight (and keeping it off) means you stop accumulating more risk, and reduce your risk compared to what it would be if you gained more weight. So losing weight does help, both with cancer risk and your general health.

But this doesn’t fully answer our question: can an increased risk go back down to the level it would have been had the extra weight never been there?

Weight loss through surgery

One of the most effective, although extreme, ways for people who are very overweight to lose weight is bariatric surgery. This covers a range of surgical techniques, such as stomach stapling or surgically bypassing large parts of the gut.

Because people lose a lot of weight after surgery, and keep most of it off, it’s more likely researchers will find an effect on cancer risk if it’s there.

It’s also more likely any effect would be due to weight loss itself, rather than lifestyle changes that reduce cancer risk. These studies also help untangle the effects of losing weight intentionally and weight loss due to illness.

Results from studies post-surgery are mixed, but overall they suggest that people who undergo bariatric surgery do have a reduced risk of cancer compared to those who don’t.

The strongest evidence so far is for women, but evidence is growing in men too.

A study that combined the results of 6 others found a staggering 45% reduction in cancer risk among formerly obese people who had bariatric surgery. But when they split the results by gender, this finding only remained in women.

A more recent US study, which included over 2500 cancer cases, also found a reduction in cancer risk in people who had surgery based on 3.5 years of follow up. And the reduced risk was seen for a range of cancers, including breast, colon, pancreatic and womb.

So the results so far are promising, and suggest weight loss can reverse increased cancer risk.

But there are limitations. Firstly, major surgery isn’t the solution for everyone. And it’s possible that people who have surgery differ in ways these studies don’t account for. And weight loss through surgery could have different effects to weight loss by other means.

Weight loss outside the operating room

A 2012 review looked at 6 weight loss studies and 5 of these linked intentional weight loss with a reduced risk of cancer.

But a more recent study, looking at the results of weight loss trials (mostly low-fat diets), didn’t find they reduced cancer risk. But the quality of evidence for cancer was rated as very low – overall the original trials only included a small number of cancer cases (103 in total) and the average amount of weight lost after 3 years was small.

These findings illustrate how difficult it is to study weight loss in the real world. So the evidence isn’t as strong. But what’s there is promising, although as with surgery studies the strongest evidence is for women – specifically for breast cancer.

How might weight loss help?

A rigorous 2016 review of how extra fat affects the body found good evidence that intentional weight loss affects key ways obesity is thought to cause cancer: namely hormones and inflammation.

And studies since have also found this.

But we don’t yet fully understand all the ways obesity causes cancer. So there’s still more to know about how weight loss could reverse these effects.

Why is there seemingly more of an effect in women?

There are many possible explanations. It could be that because these female cancers are common, there are more cases to study. This increases the chance of finding an effect if it’s there.

But it’s also possible that cancers strongly linked to sex hormones, such as womb and breast, are more quickly affected by weight loss, whereas for other cancers it may take longer to see an effect. For example, weight loss can quickly reduce levels of oestrogen in the body, and high levels of oestrogen are almost certainly how obesity causes womb and breast cancer.

Cancers more common in men, such as bowel cancer, may take longer to see an effect. This might explain why this study showed no impact of weight loss on bowel cancer risk after 7 years of follow up. This study also couldn’t distinguish between intentional and unintentional weight loss.

What’s likely is that weight loss affects different parts of the body in different ways, and this is reflected in how it might affect cancer risk. This makes sense, as weight gain affects cancer risk differently for different cancers. Studies in the future will need to take this into account.

Prevention is still best, but weight loss is worth it

So, the answer to our original question – does losing weight reduce cancer risk? – seems to be: yes.

If you are overweight, you can reduce your risk by avoiding gaining more weight.

And overall, all the research carried out so far suggests that an increased risk can start to fall with weight loss.

Plus, the best way to lose weight for most people is by eating and drinking healthily and moving more, all of which can reduce the risk of cancer independently.

But the fact remains that losing weight and keeping it off can be incredibly hard. So this must be supported by public health measures (like the sugary drinks tax) that make healthy choices easy for everyone, both to prevent weight gain, and to help those lose it who need to.

Never gaining extra weight in the first place is still best for reducing cancer risk. But we know that’s not possible for everyone – and it doesn’t help people who have already gained weight. So having evidence that weight loss could help is good news.

Emma Shields is a senior health information officer at Cancer Research UK

from Cancer Research UK – Science blog http://ift.tt/2ESxde3

What are star trails, and how can I capture them?

Star trails over the planned site of the Giant Magellan Telescope in the Atacama Desert in Chile. Image via Yuri Beletsky Nightscapes.

Star trails are the continuous paths created by stars, produced during long-exposure photographs, as shown on this page. In other words, the camera doesn’t track along with the stars’ apparent motion as night passes. Instead, the camera stays fixed, while, as the hours pass, the stars move. The resulting photos show the nightly movement of stars on the sky’s dome.

Star trails reflect Earth’s rotation, or spin, on its axis. The Earth rotates full circle relative to the backdrop stars in a period of about 23 hours and 56 minutes. So, as seen from Earth, all the stars go full circle and return to the same place in sky after this period of time, which astronomers call a sidereal (stellar) day.

View larger. | Star trails (plus meteor) photo taken by Guy Livesay. Thank you, Guy! If you aim your camera northward in a long-exposure photo, the star trails will be seen to track around the north celestial pole. In fact, the stars move counter-clockwise around the sky’s north pole in the course of every night.

Montauk Point lighthouse. Photo via Neeti Kumthekar.

What this means is that, if you’re standing out under the stars, you see them move across the sky as night passes. Stars rise in the east, arc across the sky and set in the west, just as the sun does.

Stars near the celestial poles produce the smallest circles while those near the celestial equator produce the largest. The stars – like the sun during the daytime – move from east to west across the sky each and every night. Each and every star moves 15 degrees westward in one hour.

Star trails are really arcs, or partial circles, whose ever-circling motions forever tabulate the great passage of time.

Sometimes you can get cool non-star effects into your shot, as Michael A. Rosinski did in this photo.

Ken Christison captured these glorious star trails around Polaris, the North Star. He wrote, “For the most common and often the most spectacular star trails, you want to locate Polaris and compose the image so it is centered horizontally and hopefully you can have a bit of foreground for reference.”

EarthSky Facebook friend Ken Christison has some wonderful photos of star trails. He said the equipment needed for making startrails is pretty simple:

First, a camera that allows manual settings so you can set your f/stop and shutter speeds, as well as ISO.

Next, a wide angle lens, the wider the better.

A good steady tripod is a must.

Some cameras will have a built in intervalometer which can be set to shoot the desirable number of frames. In some cases the intervalometer has a bit of lag between shots, which is the reason I use a separate, remote attached to the camera that holds the shutter down and when the camera is set in continuous shooting mode will shoot 100 frames in succession with very little gap.

The remote I use is a simple one that can be found on eBay and uses a couple AAA batteries that last quite a while. I just use the remote controller attached to the 10 pin connector. There is no need to use the wireless receiver in this case.

I use a shutter speed of 30 seconds, ISO of 400 to 800, and with my 14-24mm lens at 14mm, shoot it wide open at f/2.8.

Next, he said, you’re ready to capture your star trail:

Make sure the camera is level, and after focusing on a star, make sure the autofocus is turned off. Then, using the settings mentioned above, click the shutter and stay around long enough to know that the shutter is actually actuating. I normally go back in the house, set the timer on our kitchen stove for 45 minutes, and do other things while the camera does its work.

When the timer sounds, go back out and reset the remote by turning it off, waiting for the shutter to close, then reset quickly.

Finally, you’ll want to process your photo. Ken said:

This is one of the most important elements in making star trail images. The program I use is free, works well and is simple to use: http://www.startrails.de/html/software.html.

One other program that I have heard works well and is also free is StarStax: http://www.markus-enzweiler.de/software/software.html.

Thank you, Ken!

Visit Ken Christison’s Flickr page.

Read more: Long exposure star trail photography

A 2-hour-and-15-minute star trail image from March 21, 2014. Our friend Ken Christison in North Carolina captured this image. Want to see what a single frame of this image looked like? See the photo below.

A single frame of the star trail image above, with the elements labeled. Thank you, Ken Christison of Conway, North Carolina!

Composite image of star trails over Baja, California, from EarthSky Facebook friend Sergio Garcia Rill. This image is the product of 80 separate photographs. Thank you, Sergio!

You can also create a star trail of sorts with our local star, the sun. EarthSky Facebook friend Matthew Chin in Hong Kong created this sun trail on October 5, 2013. Thank you, Matthew!

View larger. | Or you can create a moon trail. Star trails and moon trail over Monument Valley from Victor Goodpasture. The bright object is the moon. See more from Victor at Professional Digital Photography on Facebook.

Bottom line: Star trails are the continuous paths created by stars, produced during long time exposure photographs, as shown in the photos on this page.

from EarthSky http://ift.tt/2cdDIYy

Star trails over the planned site of the Giant Magellan Telescope in the Atacama Desert in Chile. Image via Yuri Beletsky Nightscapes.

Star trails are the continuous paths created by stars, produced during long-exposure photographs, as shown on this page. In other words, the camera doesn’t track along with the stars’ apparent motion as night passes. Instead, the camera stays fixed, while, as the hours pass, the stars move. The resulting photos show the nightly movement of stars on the sky’s dome.

Star trails reflect Earth’s rotation, or spin, on its axis. The Earth rotates full circle relative to the backdrop stars in a period of about 23 hours and 56 minutes. So, as seen from Earth, all the stars go full circle and return to the same place in sky after this period of time, which astronomers call a sidereal (stellar) day.

View larger. | Star trails (plus meteor) photo taken by Guy Livesay. Thank you, Guy! If you aim your camera northward in a long-exposure photo, the star trails will be seen to track around the north celestial pole. In fact, the stars move counter-clockwise around the sky’s north pole in the course of every night.

Montauk Point lighthouse. Photo via Neeti Kumthekar.

What this means is that, if you’re standing out under the stars, you see them move across the sky as night passes. Stars rise in the east, arc across the sky and set in the west, just as the sun does.

Stars near the celestial poles produce the smallest circles while those near the celestial equator produce the largest. The stars – like the sun during the daytime – move from east to west across the sky each and every night. Each and every star moves 15 degrees westward in one hour.

Star trails are really arcs, or partial circles, whose ever-circling motions forever tabulate the great passage of time.

Sometimes you can get cool non-star effects into your shot, as Michael A. Rosinski did in this photo.

Ken Christison captured these glorious star trails around Polaris, the North Star. He wrote, “For the most common and often the most spectacular star trails, you want to locate Polaris and compose the image so it is centered horizontally and hopefully you can have a bit of foreground for reference.”

EarthSky Facebook friend Ken Christison has some wonderful photos of star trails. He said the equipment needed for making startrails is pretty simple:

First, a camera that allows manual settings so you can set your f/stop and shutter speeds, as well as ISO.

Next, a wide angle lens, the wider the better.

A good steady tripod is a must.

Some cameras will have a built in intervalometer which can be set to shoot the desirable number of frames. In some cases the intervalometer has a bit of lag between shots, which is the reason I use a separate, remote attached to the camera that holds the shutter down and when the camera is set in continuous shooting mode will shoot 100 frames in succession with very little gap.

The remote I use is a simple one that can be found on eBay and uses a couple AAA batteries that last quite a while. I just use the remote controller attached to the 10 pin connector. There is no need to use the wireless receiver in this case.

I use a shutter speed of 30 seconds, ISO of 400 to 800, and with my 14-24mm lens at 14mm, shoot it wide open at f/2.8.

Next, he said, you’re ready to capture your star trail:

Make sure the camera is level, and after focusing on a star, make sure the autofocus is turned off. Then, using the settings mentioned above, click the shutter and stay around long enough to know that the shutter is actually actuating. I normally go back in the house, set the timer on our kitchen stove for 45 minutes, and do other things while the camera does its work.

When the timer sounds, go back out and reset the remote by turning it off, waiting for the shutter to close, then reset quickly.

Finally, you’ll want to process your photo. Ken said:

This is one of the most important elements in making star trail images. The program I use is free, works well and is simple to use: http://www.startrails.de/html/software.html.

One other program that I have heard works well and is also free is StarStax: http://www.markus-enzweiler.de/software/software.html.

Thank you, Ken!

Visit Ken Christison’s Flickr page.

Read more: Long exposure star trail photography

A 2-hour-and-15-minute star trail image from March 21, 2014. Our friend Ken Christison in North Carolina captured this image. Want to see what a single frame of this image looked like? See the photo below.

A single frame of the star trail image above, with the elements labeled. Thank you, Ken Christison of Conway, North Carolina!

Composite image of star trails over Baja, California, from EarthSky Facebook friend Sergio Garcia Rill. This image is the product of 80 separate photographs. Thank you, Sergio!

You can also create a star trail of sorts with our local star, the sun. EarthSky Facebook friend Matthew Chin in Hong Kong created this sun trail on October 5, 2013. Thank you, Matthew!

View larger. | Or you can create a moon trail. Star trails and moon trail over Monument Valley from Victor Goodpasture. The bright object is the moon. See more from Victor at Professional Digital Photography on Facebook.

Bottom line: Star trails are the continuous paths created by stars, produced during long time exposure photographs, as shown in the photos on this page.

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How many stars can you see?

Sergio Garcia Rill wrote: “A west Texas sky from Mt. Locke in the Davis mountains near the McDonald Observatory … Even from this remote location, you can see the light coming from Fort Davis on the bottom of the image.”

What if you were far away from city lights, on a night with no moon and no clouds or haze. How many stars could you see with your unaided eye?

There’s really no definitive answer to this question. No one has counted all the stars in the night sky, and astronomers use different numbers as theoretical estimates.

Considering all the stars visible in all directions around Earth, the upper end on the estimates seems to be about 10,000 visible stars. Other estimates place the number of stars visible to the eye alone – surrounding the entire Earth – at more like 5,000. At any given time, half of Earth is in daylight. So only half the estimated number – say, between 5,000 and 2,500 stars – would be visible from Earth’s night side.

Plus, another fraction of those visible stars would be lost in the haze all around your horizon.

Chirag Upreti wrote on February 17, 2018: “Milky Way core, first light for 2018! A fortunate break in the weather coincided with a favorable moon phase today early morning. Impossible to resist, a buddy and I drove 3 hours to get to Montauk, the easternmost tip of New York State and the location of the Montauk Point Lighthouse. The night sky here is rated a Bortle Scale 4 (rural dark sky).”

Why can’t astronomers agree on the number of visible stars? It’s because we don’t all see the sky in the same way. Even under ideal conditions, there’s a fair amount of variation between how well people can see the stars – depending on things like the strength of your vision – and your age. As you get older, for example, your eyes become much less sensitive to faint light.

You also have to take into account the brightness of your night sky. Even on a moonless night, the glow of lights from Earth’s surface brightens the sky.

Still – far from city lights – under absolutely perfect conditions of darkness and sky clarity – a young to middle-aged person with normal vision should be able to see thousands of stars.

RodNell Barclay caught this image of the Milky Way in mid-February, 2018, while coming down from Ben Vrackie, a mountain in Scotland.

Bottom line: Estimates for the number of stars you can see with the eye alone on a dark moonless night vary, partly because eyesight and sky conditions vary.

Visit the International Dark-Sky Association

What Major World Cities Look Like at Night, Minus the Light Pollution

from EarthSky http://ift.tt/2ETNdZm

Sergio Garcia Rill wrote: “A west Texas sky from Mt. Locke in the Davis mountains near the McDonald Observatory … Even from this remote location, you can see the light coming from Fort Davis on the bottom of the image.”

What if you were far away from city lights, on a night with no moon and no clouds or haze. How many stars could you see with your unaided eye?

There’s really no definitive answer to this question. No one has counted all the stars in the night sky, and astronomers use different numbers as theoretical estimates.

Considering all the stars visible in all directions around Earth, the upper end on the estimates seems to be about 10,000 visible stars. Other estimates place the number of stars visible to the eye alone – surrounding the entire Earth – at more like 5,000. At any given time, half of Earth is in daylight. So only half the estimated number – say, between 5,000 and 2,500 stars – would be visible from Earth’s night side.

Plus, another fraction of those visible stars would be lost in the haze all around your horizon.

Chirag Upreti wrote on February 17, 2018: “Milky Way core, first light for 2018! A fortunate break in the weather coincided with a favorable moon phase today early morning. Impossible to resist, a buddy and I drove 3 hours to get to Montauk, the easternmost tip of New York State and the location of the Montauk Point Lighthouse. The night sky here is rated a Bortle Scale 4 (rural dark sky).”

Why can’t astronomers agree on the number of visible stars? It’s because we don’t all see the sky in the same way. Even under ideal conditions, there’s a fair amount of variation between how well people can see the stars – depending on things like the strength of your vision – and your age. As you get older, for example, your eyes become much less sensitive to faint light.

You also have to take into account the brightness of your night sky. Even on a moonless night, the glow of lights from Earth’s surface brightens the sky.

Still – far from city lights – under absolutely perfect conditions of darkness and sky clarity – a young to middle-aged person with normal vision should be able to see thousands of stars.

RodNell Barclay caught this image of the Milky Way in mid-February, 2018, while coming down from Ben Vrackie, a mountain in Scotland.

Bottom line: Estimates for the number of stars you can see with the eye alone on a dark moonless night vary, partly because eyesight and sky conditions vary.

Visit the International Dark-Sky Association

What Major World Cities Look Like at Night, Minus the Light Pollution

from EarthSky http://ift.tt/2ETNdZm

What’s the most distant human object from Earth?

On February 14, 1990, Voyager 1’s cameras pointed back toward the sun and took a series of pictures of the sun and the planets, making the first ever “portrait” of our solar system as seen from the outside. At that time, Voyager 1 was approximately 4 billion miles (6 billion km) away. Read more.

The most distant human-made object is the spacecraft Voyager 1, which – in late February 2018 – is over 13 billion miles (21 billion km) from Earth. Voyager 1 and its twin, Voyager 2, were launched 16 days apart in 1977. Both spacecraft flew by Jupiter and Saturn. Voyager 2 also flew by Uranus and Neptune. Now both Voyagers are heading out of our solar system, into the space between the stars. Voyager 1 officially became the first earthly craft to leave the solar system, crossing the heliopause, in 2012.

Both Voyager spacecraft were designed back in the early 1970s. They were built to take advantage of a rare grouping of planets on a single side of the sun in our solar system. This grouping, which happens only every 176 years, let the Voyagers slingshot from one planet to the next, via gravitational assists.

Source SPACE.com.

The Voyagers began acquiring images of Jupiter in January 1979. Voyager 1 completed its Jupiter encounter in early April of that year. Voyager 2 picked up the baton in late April and its encounter continued into August. The two spacecraft took more than 33,000 pictures of Jupiter and its five major satellites.

And then the Voyagers went further. When they were launched, no spacecraft had gone as far as Saturn, which is 10 times as Earth’s distance from the sun. The four-year journey to Saturn was thus a major leap, with the Voyagers arriving Saturn nine months apart, in November 1980 and August 1981. Voyager 1 then began leaving the solar system, and Voyager 2 went on to an encounter with Uranus in January 1986 and with Neptune in August 1989.

Click here for images Voyager took of Jupiter

Click here for images Voyager took of Saturn

Click here for Voyager 2 images of Uranus.

Click here for Voyager 2 images of Neptune.

View larger. | Voyager 1’s trajectory in Earth’s sky from 1977-2030. Image via Tomruen/ Wikimedia Commons/ based on data exported from NASA.

Ed Stone – who was Project Scientist for the Voyager mission – told EarthSky some years ago:

We built the spacecraft with enough redundancy – that is backup systems – so that they could keep going.

And keep going they did! The Voyagers have now been traveling for 41 years.

In 2017, astronomers described using the Hubble Space Telescope to look along the Voyagers paths. In about 40,000 years, long after both spacecraft are no longer operational, Voyager 1 will pass within 1.6 light-years of the star Gliese 445, in the constellation Camelopardalis. Meanwhile, Voyager 2 is about 10.5 billion miles (17 billion km) from Earth. Voyager 2 will pass 1.7 light-years from the star Ross 248 in about 40,000 years.

Read more: Hubble peers along Voyagers’ future paths

View larger. | Artist’s concept of the paths of the Voyager 1 and 2 spacecraft on their journey through our solar system and out into interstellar space. Image via NASA, ESA, and Z. Levay (STScI). Read more about this image.

Bottom line: Voyager 1 and its twin, Voyager 2, were launched 16 days apart in 1977. Voyager 1 is now the most distant spacecraft from Earth.

Mission status: Where are the Voyagers?

from EarthSky http://ift.tt/2F3dFCZ

On February 14, 1990, Voyager 1’s cameras pointed back toward the sun and took a series of pictures of the sun and the planets, making the first ever “portrait” of our solar system as seen from the outside. At that time, Voyager 1 was approximately 4 billion miles (6 billion km) away. Read more.

The most distant human-made object is the spacecraft Voyager 1, which – in late February 2018 – is over 13 billion miles (21 billion km) from Earth. Voyager 1 and its twin, Voyager 2, were launched 16 days apart in 1977. Both spacecraft flew by Jupiter and Saturn. Voyager 2 also flew by Uranus and Neptune. Now both Voyagers are heading out of our solar system, into the space between the stars. Voyager 1 officially became the first earthly craft to leave the solar system, crossing the heliopause, in 2012.

Both Voyager spacecraft were designed back in the early 1970s. They were built to take advantage of a rare grouping of planets on a single side of the sun in our solar system. This grouping, which happens only every 176 years, let the Voyagers slingshot from one planet to the next, via gravitational assists.

Source SPACE.com.

The Voyagers began acquiring images of Jupiter in January 1979. Voyager 1 completed its Jupiter encounter in early April of that year. Voyager 2 picked up the baton in late April and its encounter continued into August. The two spacecraft took more than 33,000 pictures of Jupiter and its five major satellites.

And then the Voyagers went further. When they were launched, no spacecraft had gone as far as Saturn, which is 10 times as Earth’s distance from the sun. The four-year journey to Saturn was thus a major leap, with the Voyagers arriving Saturn nine months apart, in November 1980 and August 1981. Voyager 1 then began leaving the solar system, and Voyager 2 went on to an encounter with Uranus in January 1986 and with Neptune in August 1989.

Click here for images Voyager took of Jupiter

Click here for images Voyager took of Saturn

Click here for Voyager 2 images of Uranus.

Click here for Voyager 2 images of Neptune.

View larger. | Voyager 1’s trajectory in Earth’s sky from 1977-2030. Image via Tomruen/ Wikimedia Commons/ based on data exported from NASA.

Ed Stone – who was Project Scientist for the Voyager mission – told EarthSky some years ago:

We built the spacecraft with enough redundancy – that is backup systems – so that they could keep going.

And keep going they did! The Voyagers have now been traveling for 41 years.

In 2017, astronomers described using the Hubble Space Telescope to look along the Voyagers paths. In about 40,000 years, long after both spacecraft are no longer operational, Voyager 1 will pass within 1.6 light-years of the star Gliese 445, in the constellation Camelopardalis. Meanwhile, Voyager 2 is about 10.5 billion miles (17 billion km) from Earth. Voyager 2 will pass 1.7 light-years from the star Ross 248 in about 40,000 years.

Read more: Hubble peers along Voyagers’ future paths

View larger. | Artist’s concept of the paths of the Voyager 1 and 2 spacecraft on their journey through our solar system and out into interstellar space. Image via NASA, ESA, and Z. Levay (STScI). Read more about this image.

Bottom line: Voyager 1 and its twin, Voyager 2, were launched 16 days apart in 1977. Voyager 1 is now the most distant spacecraft from Earth.

Mission status: Where are the Voyagers?

from EarthSky http://ift.tt/2F3dFCZ