Posted on by VirtualAstro

Beginner’s Guide To Binoculars

Credit: opticsreviewer.com

Before you consider buying expensive equipment for viewing the wonders of the night sky, binoculars are one piece of equipment every amateur astronomer should have.

Many beginners to astronomy (especially around the holiday period) are sometimes dead-set on getting a telescope, but many aren’t aware that a good pair of binoculars can outperform many entry level telescopes for a similar cost, or much less.

Binoculars are simplicity in themselves — maintenance free, instantly available for use and very versatile, as they can be used for daytime, or “terrestrial viewing” just as well. It is difficult to say the same for with most telescopes.

Go into any photographic store, or website that sells binoculars and you will be met with literally hundreds of different makes, types and sizes – confusing for the beginner, but with a few pointers it can be easy to choose.

Credit: astronomybinoculars.com

So how do you choose a pair of binoculars that will give good results with astronomy?

When choosing binoculars for astronomy, the only variables you need to think about are size of the optics and weight.

Too small and they won’t be powerful enough or let enough light in; too big and heavy means they are almost impossible to use without a support or tripod. Beginners need to find a pair of binoculars which are just right.

The key is to get as much light into the binoculars as possible without making them too heavy. This will give sharp views and comfort when used.

Size and weight come hand in hand, the more light gathered, the heavier the binoculars will be.

All binoculars are measured or rated by two numbers, for example: 10 X 25 or 15 X 70. The first number is the magnification and the second number is the “objective diameter” which is the diameter of the objective lens and this determines how much light can be gathered to form an image.

Credit: Halfblue Wikipedia

The second number or objective diameter is the most important one to consider when buying binoculars for astronomy, as you need to gather as much light as possible.

As a rule of thumb, binoculars with an objective diameter of 50mm or more are more suited to astronomy than smaller “terrestrial” binoculars. In many cases a larger objective also gives better eye relief (larger exit pupil) making the binoculars much more comfortable to use.

For the beginner or general user, don’t go too big with the objective diameter as you are also making the binoculars physically larger and heavier. Large binoculars are fantastic, but — again — almost impossible to keep steady without a support or tripod.

Celestron Skymaster 15 X 70 Binoculars

Good sizes of binoculars for astronomy start at around or just under 10 X 50 and can go up to 20 X 80, but any larger and they will need to be supported when using them. Some very good supported binoculars have objective diameters of more than 100mm. Theses are fantastic, but not as portable as their smaller counterparts.

Binoculars are one of the most important items a new or seasoned astronomer can buy. They are inexpensive, easy to choose, use and will last a very long time.

Enjoy your new binoculars!

Posted on by VirtualAstro

The Holidays Are Coming! A Beginner’s Guide to Telescopes

The holidays are fast approaching, and you may be looking for gift ideas for your friends, loved ones and even yourself. Are you considering buying a telescope this year?

There are many different types of astronomical telescope available on the market and for the beginner, selecting one can be a bewildering experience. Before buying a telescope it is important to ask yourself: What objects do you want to see through your new telescope and how much can the person buying it afford to pay?

Not all telescopes are the same nor do they give the same results. Many amateur astronomers have two or more different telescopes for different types of observing, but there are some which offer a good compromise and most objects can be seen through them.

Once you have decided on the telescope’s main purpose and what you want to see through it, choosing one can become much easier. With the exception of the Moon, planets and close star clusters, interesting night sky objects are faint; in fact most will appear as just points of light. As a new observer you may be mainly interested in viewing the Moon and planets, and if this is the case, a telescope with a small objective (primary mirror or lens) may be sufficient.

Most observers quickly graduate to galaxies, nebulae, globular clusters, open clusters etc. To view these objects you will require a telescope with the largest aperture that is possible for your circumstances, which includes things like cost, weight, portability, etc.

Below are the 3 main types of telescope worth considering as a beginner:

Newtonian reflector telescopes are a popular choice for astronomical use because they have the lowest cost per inch of aperture. Observations of faint deep sky objects, such as Galaxies and Nebulae, can be achieved at a relatively reasonable cost by reflectors with mirror diameters of 150 to 200mm (6 to 8 inches).

Celestron Astromaster 130

Refractor telescopes are good for achieving high power and contrast when viewing the planets and the moon. They have a reputation of providing crisp, sharp-quality images. Since they are virtually maintenance free, they are easy to operate, but due to high costs for the large aperture scopes, most beginners will choose a Newtonian reflector as a first scope for all round astronomy. Short-tube refractors are now another low cost option for beginners. Their smaller size makes them an excellent choice for a portable telescope and the beautiful wide-field star vistas which they provide are great for learning your way around the night sky.
Bresser Refractor Telescope

Dobsonian Telescopes are one of the best choices for a general telescope and have many advantages including simplicity, economy and large light gathering ability. Dobsonians are actually large Newtonian telescopes on a simple manual Alt/ Az (Up, down, side to side) mount. Due to the mount and optical tube assembly being so simple, Dobsonian telescopes are the most economical on a cost per inch basis. This enables massive apertures being made affordable, bringing fainter objects within the grasp of the amateur and usually well within budget with mirror diameters from 150mm to 400mm (6 to 16 inches) or much larger.
Dobsonian Telescope
The Meade 16" LightBridge

Another consideration when choosing a telescope is the mount – the part the optical tube assembly sits on. Usually a tripod with a head containing manual or motorised controls, which point the telescope and track an object observed.

The three main types are:

Equatorial – Usually found paired with all telescopes apart from Dobsonians. Equatorial mounts enable the telescope to follow the rotation of the sky with on axis parallel to the Earth’s axis of rotation. They can also be used in a basic manual mode which can be manually moved by hand in the Altitude (up/down) and Azimuth (left/right) axis. Many higher end mounts have computers and GoTo systems incorporated which are almost essential for astrophotography.

Hand operated Manual Alt/ Az (Altitude/ Azimuth) – Usually found on very cheap or small telescopes, Dobsonian telescopes, binocular mounts and photographic tripods. Simple and easy to use, however they do not track objects across the sky.

GoTo or Computerised – Found on many mid to high range telescopes of all sizes and extremely popular with astrophotographers and imagers. Unfortunately many beginners are drawn to the sexy marketing of scopes that are computerised and this can be an expensive mistake. Personally I believe it to be better to use manually guided telescopes when starting out instead of jumping in straight away with computerised ones. It is much better to concentrate on good optics and a solid mount rather than waste lots of money on often complicated and unnecessary electronics. For more info on mounts and GoTo Systems see the Beginners Guide to GoTo

Hopefully this guide has given you more insight into the complicated world of telescopes, and enable you to make a better decision when buying your new telescope. Your new purchase should be one that you can enjoy and get the most out of for many years.

Posted on by Nancy Atkinson

ROSAT Satellite has Re-Entered; No Reports of Debris

Initial reports said ROSAT fell sometime during this track. Credit: DLR and ROSAT_Reentry Twitter.

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It’s official: the ROSAT satellite has come down. The Deutsches Zentrum für Luft- und Raumfahrt (DLR), the German Space Agency confirmed the satellite plunged to Earth sometime between 1:45 UTC and 2:15 UTC on Oct. 23, 2011 (between 8:45 and 9:15 EDT Oct. 22) There is currently no confirmation if pieces of debris have reached Earth’s surface.

Update: US Strategic Command estimates an entry time of 1:50 UTC +/- 7 Minutes. This entry time would put the satellite in the Indian Ocean, and not over China as reported below. The DLR said that after further analysis they should be able to provide more information about exactly where the debris hit.

The @ROSAT_Reentry Twitter feed posted the picture above, indicating the satellite’s fall occurred sometime during the groundtrack shown.

Other reports via Twitter from skywatchers around the world had no sightings of any lit debris falling, or any actual sightings of the satellite passing overhead since 23:30 UTC on Oct. 22. Some news reports say it could have re-entered over China, but it likely didn’t make it as far as Korea or Japan.

We’ll provide more information when it becomes available.

ROSAT Satellite. Credit: DLR

Posted on by VirtualAstro

ROSAT – Fiery Debris To Rain From The Sky

ROSAT Credit: NASA

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The recent re-entry of the UARS satellite was not the end of falling satellite debris, as the German ROSAT X-ray observatory satellite will soon crash back to Earth.

Last month NASA’s large UARS satellite re-entered the atmosphere and burned up over the Pacific Ocean, with about 500 kg of debris falling into the water. But the smaller Roentgen Satellite or ROSAT will have approximately 30 pieces equaling 1.5 tons that will resist burn up and make it to the surface.

The largest piece of the satellite expected to reach the surface is the heat-resistant, 32 inch, 400 kg mirror.

Compared to UARS, there is an increased chance of someone being hit by a piece of the falling debris. The odds have been estimated as a 1 in 2,000; UARS was 1 in 3,200.

As with UARS, it is unknown where ROSAT will burn up and where its remaining parts will impact the surface, however the satellite is expected to re-enter between the 21st and 24th of October. The Center for Orbital and Re-Entry Debris studies predicts October 23, 2011 a 06:40 UTC ± 30 hours.

For up to date predictions check the Centre for Orbital and Re-Entry Debris Studies.

Prediction Ground Track Credit: Center for Orbital and Reentry Debris Studies

Until then, you can keep an eye out for the small satellite as it is a naked eye object. It’s nowhere near as bright as the ISS, but it is visible. Check Heavens Above or Spaceweather for predictions of when it will pass over your location.

The 2.4 ton Roentgen Satellite (ROSAT) was launched by NASA in 1990 as a joint venture between Germany, Britain and the USA.

The satellite was designed to catalogue X-ray sources in deep space and mapped around 110,000 stars and supernovae. It also discovered that some comets emit X-rays. It was permanently damaged in 1998, and its mission was officially ended in February of 1999.

ROSAT will soon meet its fiery end; will you see it pass over before then?

Keep an eye out for that falling mirror.

Credit: NASA
Posted on by Tammy Plotner

Wake Up! The Orionid Meteor Shower Peaks On October 20…

Orionid Meteor Shower: The above image shows brilliant multiple meteor streaks that can all be connected to a single point in the sky just above the belt of Orion, called the "radiant." The Orionids take place in mid-October and the parent comet is Halley. Comet Halley is actually responsible for two known meteor showers: The other is the Eta Aquarids, which are visible every May. Image Credit and Copyright: Tunc Tezel

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Do you hate to get up early? Then stay up late, because it’s infrequent that both the northern and southern hemispheres have a chance to catch an annual meteor shower. Right now the Earth is heading into the complex Orionid stream, and while the skies won’t be perfectly dark, they aren’t going to be bad. Where and when do you watch? Follow me…

As the Earth slowly orbits the Sun, it passes into one of the debris streams left by Comet Halley and the material returns as the Orionid meteor shower. While it won’t be a “meteor storm”, what you can expect to see is one of the most predictable and reliable meteor showers of the year. Even if it’s a few days early (or late), take advantage of any clear skies and begin your observations because activity is up.

The Orionids produce an average of 10-20 meteors per hour maximum, and best activity begins before local midnight on October 20th, and reaches its peak as Orion stands high to the south about two hours before local dawn on October 21st. With only partial slice of Moon in the late evening/early morning, this looks to be the year’s last, best meteor shower!

“Every year around this time Earth glides through a cloud of dusty debris from Halley’s Comet,” explains Bill Cooke of the NASA Marshall Space Flight Center. “Bits of dust, most no larger than grains of sand, disintegrate in Earth’s atmosphere and become shooting stars.”

“It’s not an intense shower,” he says, “but it is a pretty one.”

Although Comet Halley has now departed the inner Solar System, its debris trail remains well organized – allowing us to predict when this meteor shower will occur. The Earth first enters the stream at the beginning of October and does not leave until the beginning of November. This makes your chances of “catching a falling star” above average!

“Earth comes close to the orbit of Halley’s Comet twice a year, once in May and again in October,” explains Don Yeomans, manager of NASA’s Near-Earth Object Program at the Jet Propulsion Laboratory. Orionid meteoroids strike Earth’s atmosphere traveling 66 km/s or 148,000 mph,” he continued. These meteors are very fast, and although faint (average magnitude 3), occasional fireballs do leave persistent trails that shimmer in the upper atmosphere. It’s the “Oooooh!” effect!

For best success, get away from city lights. Face south-southeast in the northern hemisphere and almost overhead in the southern – then relax and enjoy the stars of the Winter Milky Way. The radiant is near Betelguese, but may occur from any part of the sky. When the Moon rises, try positioning yourself so a house, tree, or other obstruction helps to reduce the glare. The meteor watching experience is much more comfortable if you include a reclining lawn chair, blanket, and thermos of your favorite beverage. Nothing spoils watching quicker than “meteor neck”.

Clouded out? Don’t despair. You don’t always need eyes or perfect weather to keep the watch. Tune an FM radio to the lowest frequency that doesn’t receive a clear signal. An outdoor FM antenna pointed to the zenith increases your chances – but isn’t essential. Simply turn up the static and listen. Those hums, whistles, beeps, bongs, and occasional snatches of signals are distant transmissions being reflected off a meteor’s ion trail!

Posted on by Ray Sanders

Why is Tonight’s Full Moon the Smallest of the Year?

Moon at Perigee and Apogee. Credit NASA

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Think we can only see half of the Moon’s surface from Earth? Not always.

Over the course of the year, observers on Earth can view a bit less and a bit more than half of the lunar surface. Additionally, the Moon appears smaller in the sky during some months compared to other times of the year.

Due to the processes at work, tonight’s full Moon is an opposite of the “Supermoon” that made headlines earlier this year.

What causes our Moon to change apparent size throughout the year, and how do we notice this phenomenon?

While it would be difficult to judge the apparent size of the full Moon each month with our eyes, the phenomenon of Lunar librations is readily apparent in the animation below.

There are three forces at work that help produce the “dancing” effect as shown in the video above.

There are three types of lunar libration:

First, the Moon doesn’t orbit Earth in a perfectly circular orbit. An eccentric orbit will cause our Moon to lead and lag in its orbital position while its rotational speed stays the same. This causes a libration in longitude.

Secondly, the Moon’s rotational axis is slightly inclined to its orbital plane, with respect to Earth. The Moon’s orbit is also inclined with respect to the ecliptic, allowing the Moon to be illuminated from above and sometimes from below. The illumination from above and below allows some of the lunar surface beyond the poles to be visible from Earth.

Last but not least, there is a small daily oscillation due to Earth’s rotation. This oscillation changes the perspective at which an observer views the Moon. Imagine a straight line connecting the center of Earth with the center of the Moon. Over time an observer would be on one side of this imaginary line and then the other, which would allow the observer to look first around one side of the Moon and then around the other. This is because an observer on Earth is on the surface and not at the center of Earth.

A slight bit of Lunar trivia: Lunar librations helped notable British astronomer Patrick Moore investigate the edge regions where librations provided extra coverage. Moore’s investigations lead him to discover a large circular feature, which he named “Mare Oriental”. Once studies of the Lunar farside were performed from space, it was discovered that Mare Oriental was a lava filled impact crater.

Posted on by Ray Sanders

World Space Week ( Oct 4th – 10th ) — Join the Fun!

World Space Week - October 4th - 10th, 2011. Image Credit: World Space Week Association

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What is World Space Week?

Founded in 1981, World Space Week Association is one of the world’s oldest space education organizations. As a partner of the United Nations in the global coordination of World Space Week, WSWA recruits and supports a worldwide network of coordinators and participants. WSWA is a non-government, nonprofit, international organization, based in the United States.

World Space Week is an international celebration of science and technology, and how each benefits the human condition. In 1999 The United Nations General Assembly declared that World Space Week will be held each year from October 4-10, commemorating two notable space-related events:

The annual kick-off date of October 4th corresponds with the October 4th 1957 launch of the first human-made Earth satellite, Sputnik 1.

The end date of October 10th corresponds with the October 10th 1967 signing of the Treaty on Principles Governing the Activites of States in the Exploration and Peaceful Uses of Outer Space, including the Moon and Other Celestial Bodies.

Here’s some information from their F.A.Q on how you can participate in World Space Week, either by volunteering or by attending an event.

Where and how is World Space Week celebrated?

World Space Week is open to everyone – government agencies, industry, non-profit organizations, teachers, or even individuals can organize events to celebrate space. WSW is coordinated by the United Nations with the support of WSWA and local coordinators in many countries.

What are the benefits of World Space Week?

WSW educates people around the world about the benefits they receive from space and encourages greater use of space for sustainable economic development. WSW also demonstrates public support for space programs and excites children about learning and their future.
Some of the other benefits include promoting institutions around the world that are involved in space and fostering a sense of international cooperation in space outreach and education.

How can schools participate?

This event is ideal for teachers to promote student interest in science and math. To encourage participation, World Space Week Association gives various educational awards each year.

Sign at NASA's Johnson Space Center announcing World Space Week. Photo Credit: NASA/WSWA

What can I do for World Space Week?

If you’d like to become involved with WSW you can:

  • Volunteer for World Space Week Association
  • Organize an event directly
  • Help expand and coordinate World Space Week
  • Encourage teachers and students to do space-related activities
  • Become a Volunteer
  • Hold an Event During World Space Week

    • If you hold an event, be sure to add your event to the World Space Week calendar and tell the media and your regional WSW coordinator about your planned event. You can also order World Space Week posters and display them in your community.

    If you’d like to find a World Space Week event in your area, visit:http://www.worldspaceweek.org/calendar_2011.php

    You can learn more about World Space Week at: http://www.worldspaceweek.org

    Source: World Space Week Association

    Posted on by VirtualAstro

    The Draconid Meteor Shower – A Storm is Coming!

    Geminid Meteor - George Varros (courtesy NASA)

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    The Draconids are coming! Will this meteor shower produce a storm of observable meteors, or just a minor squall? The Draconid Meteor Show should begin on October 8, 2011 starting at dusk (roughly 19:00 BST) and continue through the evening. Peak activity of this normally minor and quiet shower is estimated to be at 21:00 BST (20:00 UT). There seems to be a wide range of predictions for this year’s shower, but some astronomers believe there could be up to 1,000 meteors per hour, making this a meteor storm!

    The Draconids or Giacobinids as they are also known, radiate from a point in the constellation of Draco the Dragon in the Northern hemisphere. In the past, notably in 1933 and 1946, the Draconids turned into a meteor storm with meteor rates of more than one every second!

    So, will this year bring us a storm? Astronomers believe so as the predicted path of the Earth through the debris streams of comet 21P/Giacobini-Ziner is favorable for a major storm, similar to what has been seen in previous years. Some reports say NASA is even considering the potential risk of damage to the International Space Station and other satellites due to meteroid impacts.

    Some astronomers, on the other hand, are saying this shower could be a dud, with only 5 or so meteors per hour.

    Credit: Alex Tudorica

    Observers in the UK and Northern Europe are ideally placed to see the peak of the Draconids. Unfortunately the peak occurs in the day time for North America. There will also be a bright Moon which may drown out many but the brightest meteors, but if predictions are correct, you will still see many. You may see Draconid meteors on the 7th an the 9th also, so it is worth going out and checking the skies.

    The Constellation Draco in the northern sky in the northern hemisphere.

    Draco is a circumpolar constellation visible all night from northern latitudes.

    There is no skill or even astronomical knowledge needed to enjoy meteor showers. All you need is to be comfortable, away from bright lights and your eyes. Sit back on a recliner or garden chair and fill your gaze with sky as meteors can appear anywhere as they radiate from the constellation of Draco. For more info on how to enjoy meteor showers visit meteorwatch.org

    So what will you see? Draconid meteors are usually slow and bright streaks of light, but if you look away, you can still miss them so keep your gaze on the sky.

    There are no guarantees of a meteor storm or even a good meteor shower as these phenomena can be very unpredictable, but the only way to find out is to go outside and look up.

    If predictions are correct, you could be in for a spectacular treat and something truly memorable, so don’t miss it. Even if it is cloudy, you can listen to the meteor shower or you can watch as they enter Earths atmosphere

    For more information on the Draconids, see the International Meteor Organization’s post on this year’s shower.

    Good Luck!

    Fireball Meteor
    Credit: Pierre Martin of Arnprior, Ontario, Canada.
    Posted on by VirtualAstro

    What’s That Very Bright Star – Is it the Planet Jupiter?

    Jupiter Credit: John Talbot

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    Have you seen a very bright star rising in the East every night the past few months? If you’re a night owl, you may have noticed it moves across they sky from the East into the West, shining brightly throughout the night. However this object is not a star! It’s the planet Jupiter and it is the brightest object in the night sky at the moment, apart from the Moon.

    At the end of October Jupiter will be at opposition. This means the mighty planet (the largest in our solar system) will be directly opposite the sun as seen from Earth and it will also be at its closest point to Earth in the two planets’ orbits around the Sun. This makes Jupiter or any other object at opposition appear brighter and larger. The opposition of Jupiter occurs on October 29, 2011.

    But Jupiter has been gracing our night sky for several months, and will continue to shine brightly as it moves in and out of opposition. But enjoy the view now, as this will be the closest opposition until 2022!

    Visually, even with the naked eye, Jupiter is stunning! A burning yellowish-white star-like object, many times brighter than any other stars.

    But through a pair of ordinary binoculars or a small telescope, Jupiter comes to life. Not only is it possible to see the disc of the Planet, you can also see the four Galilean moons.

    The Galilean moons, Callisto, Ganymede, Europa and Io were discovered by Galileo over 400 years ago and are amazing worlds in their own right.

    Callisto is the outermost moon with a very ancient and heavily cratered surface. It is the second largest of the four moons, but does not interact tidally with an “orbital resonance” unlike the other three moons.

    Callisto. Image credit: NASA/JPL

    Ganymede is the largest of the four moons and is also the largest moon in the Solar system, being larger than the Planet Mercury. The bizarre surface is a mix of two types of terrain – highly cratered dark regions and younger, but still ancient regions with a large array of grooves and ridges. Ganymede is the only moon in the solar system to have its own magnetosphere.

    Ganymede
    Ganymede Credit: NASA

    Europa is the second closest moon and is also the smallest. It has one of the smoothest and newest surfaces in the solar system, being covered purely with ice. Europa is likely a water world and it is believed that below its icy surface, lies a deep moon-wide ocean surrounding a warm mantle. It is one of the most likely places to harbour life in the solar system.

    Europa from Galileo
    Europa from Galileo

    Io is the innermost of the four Galilean moons of Jupiter and third largest. It is the most geologically active body in the solar system with over 400 active volcanoes and an ever changing and hostile surface of sulphur and silicates.

    Io Credit: NASA

    When you look up tonight and stare at Jupiter, or you are looking at it through binoculars or a telescope, just think – Jupiter and the four Galilean moons are a very interesting place, almost a mini solar system with our larger solar system!

    Occasionally you will see Jupiter’s “Great Red Spot” or the shadow of one of the moons on Jupiter’s surface. The Jupiter system is always changing.

    If you want to find out what the positions are for the moons, use planetarium software such as Stellarium and then have a look yourself.

    Good luck!

    Posted on by Nancy Atkinson

    Stunning New Timelapse: Tempest Milky Way

    It’s been a summer of storms across the US, and timelapse photographer Randy Halverson has taken advantage of it! Randy alerted us that he’s just put out a new video following his incredible Plains Milky Way timelapse from earlier this year. His new one is “Tempest Milky Way” which features the storms and skies of the Midwest US. Randy said he wanted to combine “good storm and star shots,” but that the opportunity doesn’t come along very often. “The storm has to be moving the right speed and the lightning can overexpose the long exposures.” But Randy’s photography and editing prowess shines in “Tempest Milky Way.”

    A few things to watch: Look for a Whitetail buck (briefly) at the 1:57 mark (“It was caught on 20 frames, and was there for about 10 minutes. It was only 50 yards from the camera, dolly and light,” Randy said.)

    At about 2:28 an airplane flies under the oncoming storm.

    At the 3:24 mark, a meteor reflects on the water of the small lake. Look for many other meteors in the timelapse, too.

    This is a wonderful video, augmented with great music, not to be missed!

    See more at Randy’s website DakotaLapse