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Bringing the Universe to Your Classroom!

Monday, August 12, 2019

Observing and Photographing Meteors

On just about any evening under a dark sky, you’re likely to see a meteor or two streaks across the starscape. They catch you by surprise, serving as a reminder that space is not static - things are moving out there, and fast. With the annual Perseid meteor show upon us, Orion Telescopes and Binoculars provides the following guide on how to successfully observe and photograph meteors.

What Are Meteors? 

Often called "shooting stars," meteors are really particles from outer space - fragments of comets and asteroids - that burn up from friction as they enter the Earth’s atmosphere. While still in space, the particles are called meteoroids. A very bright meteor is about the size of a grape; typical meteors are more the size of tiny pebbles or grains of sand. A very large meteor may break up as it penetrates the atmosphere, throwing off sparks. Occasionally, a meteor may even make noise as it shoots through the air, though this is rare. The largest meteors do not completely incinerate and actually land on Earth as rocks, called meteorites.

A fireball is a very bright meteor loosely defined as being brighter than the planet Venus, whose maximum magnitude is -4.7.

Perseid meteor shower to illuminate night sky the week of August 11th - Image by Mansfield News Journal.
Perseid meteor shower to illuminate night sky the week of August 11th - Image by Mansfield News Journal.

Ordinarily, you can see about one meteor per hour at a dark-sky location if you watch the sky continuously. These are sporadic (random) meteors, not associated with specific meteor showers. You will see more meteors after midnight since you are then on the "forward" side of the Earth as it moves along in its orbit.

Meteors En Masse - Meteor Showers 

A meteor shower happens when the Earth enters a swarm of meteoroids, usual debris from a comet that trails along in the comet’s orbit. At certain times of the year, the Earth’s orbit intersects that of a comet, and we get pelted with the debris.

Then, the meteor rate rises to 10 or 20 per hour, and possibly even 100 or more per hour at the maximum of some showers! The meteors in a shower all appear to come from the same general area in the sky. More precisely, if you trace the path of each meteor backward, you’ll find that they converge near one point in the sky. That point is called the radiant, and it is different for different showers. Each shower is named for the constellation in which its radiant is located. For example, the Perseid shower in August has its radiant in the constellation Perseus. It is often hard to tell whether a meteor belongs to a particular shower or not since even during a shower, some meteors appear far from the radiant or are moving in slightly different directions.

Because they occur at particular positions in the Earth’s orbit around the Sun, meteor showers recur on the same date every year. Most showers last two or three days; some are longer, and some are very brief.

Some meteoroid swarms have orbital periodicities of their own, so we don’t encounter them every year. For example, the Leonids were spectacular in 1933, 1966 and 2001. In the "off" years, few or no Leonid meteors are seen.

Below is a list of major showers; there are many minor ones producing smaller numbers of meteors. One major shower, the Quadrantids, is named for an obsolete constellation corresponding to part of Bootes.

Observing Meteors

Meteor watching is like fishing. You cast your sights upward, sit back, wait a while, and see if you get any bites. You’ll increase your chances by going to a dark-sky location, away from suburban light pollution. Most meteors aren’t very bright, so you’ll see more of them if you go to a dark country site. Your chances of logging meteors are also improved when the Moon is below the horizon, or during the new Moon phase, as moonlight can wash out all but the brightest fireballs.

Observing meteors is a naked-eye activity. You don’t need, or even want, a telescope or binoculars to view meteors, as these will only restrict your field of view. You want to be able to visually canvas as much of the sky as possible because meteors can flash anywhere. For scientific work, you’ll need a star chart (for plotting meteor paths) and a ruler (to hold up against the sky to note exactly where a meteor went). More important is a lawn chair and, if appropriate, blankets to keep you comfortable during your vigil.

You will notice that meteors not only differ in brightness but also in speed and length of travel. Some appear to move relatively slowly, glowing for a second or two while others streak quickly and are gone in a fraction of a second. Some of the brightest meteors leave vapor trails in the sky that can linger for several seconds after the meteor has disappeared.

While looking for meteors you’ll see plenty of airplanes and satellites, too. How do you distinguish them from meteors? For one, meteors move much faster. Another dead giveaway for an airplane is a blinking light. Binoculars will help you identify airplanes, which normally have more than one light. A satellite looks like a slowly moving star. An iridium satellite occasionally reflects sunlight so that it looks like a bright, slow meteor; however, the movement is much slower and it fades out rather than burning up suddenly.

Telescopic Meteors 

Occasionally, you’ll see a tiny, distant meteor in binoculars or a low-power telescope. These are called telescopic meteors and are so rare that you probably shouldn’t spend time looking for them — but take note when you happen to see one while viewing other things.

Photograph a Falling Star

Photographing meteors is relatively easy — if you encounter a meteor at the right place and right time! The technique is to use a DSLR or camera with a manual exposure setting using a normal or wide-angle lens (preferably f/2.8 or faster) and take a long exposure of the stars. If a bright meteor comes through the field, the camera will probably catch it.

The camera can stand on a fixed tripod (recording the stars as trails due to the Earth’s motion) or on a clock-driven telescope (to get pinpoint images of the stars). Light pollution and your local sky quality conditions will limit how long the exposure can be before the image quality degrades. Experiment with different exposures and ISO settings to determine the best results for your set-up and location.

You’ll likely catch a lot of airplane and satellite trails in your pictures, too. You can distinguish them from meteor trails by their uniform thickness (or the regular-spaced, dots from an airplane’s blinking light). A meteor trail is usually not uniformly thick, but rather almost always exhibits a bright "head" where the meteor burned up.
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Thursday, August 1, 2019

What's In The Sky - August 2019

Warm summer nights seem like they're tailor-made for backyard astronomers. Evenings throughout August are great opportunities to get the whole family outside for summer stargazing fun with a telescope or your favorite pair of binoculars. Here are a few of Orion Telescopes and Binoculars' top picks for August stargazing...

Perseid Meteor Shower 2012. Image by David Kingham.
Perseid Meteor Shower 2012. Image by David Kingham.

Perseid Meteor Shower

Go outside on the night of August 12th-13th for the best chances to see the peak of the Perseid meteor shower! Some may be visible each night from July 23rd through August 20th, but the peak is on the 12th -13th. Unfortunately, the Moon will be 12 days old at this time, which will limit visibility due to its brightness. However, with up to 80 meteors per hour expected at maximum, this is still one of the most popular meteor showers of the year.

Mercury high in the sky

On the morning of August 9th Mercury will be at its greatest Western elongation, rising early before sunrise. Because Mercury is so close to the Sun, it is best viewed during an elongation like this, since it is at its maximum separation from the Sun. Look above the Eastern horizon before sunrise to catch a glimpse of the innermost planet!

Messier 16, the Eagle Nebula imaged by Utkarsh Mishra and Zhuoqun Wu.
Messier 16, the Eagle Nebula imaged by Utkarsh Mishra and Zhuoqun Wu.

Nebulas

Many excellent examples of gaseous nebulas are on display in the skies of August. The brightest are M16 the Eagle Nebula, M17 the Swan Nebula, M20 the Trifid Nebula and the very bright M8, Lagoon Nebula. All are visible in binoculars from dark locations with good seeing. Use a small to moderate aperture telescope with the aid of an Oxygen-III eyepiece filter or SkyGlow Broadband Filter to see these nebulas from locations plagued by light pollution.

New Moon

New Moon is August 30th and therefore the best time to observe the more faint objects like galaxies and star clusters. Grab your gear and enjoy!

August Challenge Object

Orion's challenge this month is a surprisingly easy object to see with a telescope, but not so easy with binoculars. Look for M27, the Dumbbell Nebula in the constellation of Vulpecula, just south of Cygnus. M27 is one of the nearest and brightest planetary nebulas visible from Earth. It's so big that it can be spotted in humble 7 x 50 binoculars, but it does present a challenge! Try to track M27 down this August with your astronomy binoculars; it will be a small dot, slightly larger than the surrounding stars, but definitely visible through 50mm or larger binoculars.

All objects described above can easily be seen with the suggested equipment from a dark sky site, a viewing location some distance away from city lights where light pollution and when bright moonlight does not overpower the stars.
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