ALPO Meteors Section

The peak of the 1998 Leonid meteor shower (rich in bright fireballs), shown in a four-hour time exposure through a fisheye lens, and taken by Juraj Toth of Modra Observatory. This photograph demonstrates how the meteors in a particular shower appear to emanate from a certain point in the sky called the radiant. On a given night, this radiant point will remain relatively stationary with respect to the background star constellations; but will rise, traverse the sky, and set in the same manner as the sun and moon.

• Viewing Meteor Activity
• Viewing Activity from the 2009 Delta Aquariid Meteor Shower
• Viewing Activity from the 2009 Perseid Meteor Shower
• 2009 Meteor Shower Calendar
• Explanation of the 2009 Meteor Shower Calendar
• New Meteors Book Available
• Additional On-Line Resources

Viewing Meteor Activity

Since meteors are a transient phenomena one cannot go outside at night and expect to see meteor activity. This is especially true during the evening hours when the Earth is moving in the opposite direction from the sky seen above during those hours. At this time of night meteoroids (meteors in space) must catch up to the Earth in order to enter the Earth's atmosphere. Therefore meteor rates are lowest near 1800 (6:00pm) local time. Conditions for viewing meteor activity improves as the night progresses. At midnight a great majority of the meteors seen strike the Earth from a perpendicular angle instead of from behind. These conditions offer better rates than witnessed early in the evening but the general activity is still low when compared to the morning hours. During the dark morning hours the Earth is rotating toward the direction it moves in space, known as the apex. During this time the Earth slams head-on into meteoroids and many more will be seen. This is much like a vehicle driving through the rain. More raindrops will strike the front windshield compared to the rear window. The peak meteor activity occurs near 0600.

In addition to the diurnal cycle there are also annual variations in the meteor activity. As seen from the mid-northern hemisphere the second half of the year is much more active than the first six months. The reason for this are several. First of all the sporadic (random) meteor activity is stronger during this period. Also most of the major annual showers active during the second half of the year have radiants located north of the celestial equator, favoring northern obserevers. The cycle seen from the mid-southern hemisphere is opposite with the better activity occurring during the first half of the year. Observers at the equator enjoy fair, but not exceptional activity all year long.

During certain times of the year the major meteor showers are active and increase the nightly activity severalfold. This is especially true if the moon is near its new phase and not brightening the nighttime sky. The list of these showers is provided below (see the class I showers).

This is also the best time to see fireballs, which are exceptionally bright meteors that can light the nighttime scene. These meteors can range from the light of the brightest planet Venus (magnitude -5) to that beyond the light produced by the full moon (magnitude >-13).

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This double bursting fireball was photographed at 23:45 Universal Time on August 6, 2007 by Maurizio Eltri from central Venice, Italy. He estimated this sporadic (random) fireball to be of maximum magnitude -8, which is nearly as bright as the half moon. Picture courtesy of Maurizio Eltri, (Unione Astrofili Italiani Sezione Meteore).

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To keep current on the upcoming meteor activity the Meteors Section invites you to subscribe to their quarterly newsletter, available for the price of postage (currently 44 cents per issue). To subscribe contact our section coordinator Robert Lunsford.

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Viewing Activity from the 2009 Delta Aquariid Meteor Shower

The Southern Delta Aquariids (SDA's) is the strongest southern shower active during the northern hemisphere's summer months. The Earth encounters these particles from July 21st through August 30th with a broad maximum of activity occurring near July 30. Zenith hourly rates (ZHR's) average twenty near maximum activity. During July and August this radiant is well placed as it rises near 2200 local daylight time and culminates at 0300 local daylight time (LDT). This shower is visible over most of the Earth but those observers located in the southern tropical areas are best suited as the radiant passes through their zenith. Observers further south may have a lesser zenith angle but they also enjoy a longer night which allows longer observations of this activity. Northern observers have the radiant located in the southern sky. The elevation of the radiant will depend on your latitude with those located in the north tropical areas favored.

On July 30, the radiant is located at 22:42 (341) -17. This area of the sky is located in southern Aquarius, just two degrees west of the third magnitude star Delta Aquarii. An easier signpost may be the bright first magnitude star Fomalhaut (Alpha Pisces Austrinis), which lies some fifteen degrees to the southeast of the SDA radiant. These meteors strike the Earth's atmosphere with a velocity of 43 kilometers per second. Visually these meteors would appear to possess a medium speed for those shower members seen far from the radiant and high in the sky. Those seen close to the radiant or close to the horizon would appear to move slower. Most members of this shower are faint so rates seen from urban locations would most likely be unimpressive. Only from darker rural locations can this shower really be appreciated.

To view this shower it is advised that you limit your session to the morning hours when the radiant has achieved sufficient altitude. The best rates will occur near 0300 LDT when the radiant lies highest in the sky. You should face toward the southern half of the sky so that you may be able to better distinguish the SDA's from the other weaker radiants active in this same general portion of the sky. Facing this direction will also allow you to experience the swift Perseids shooting into your field of view from behind. Although not as numerous as the SDA's in July, the Perseids will provide some memorable bright meteors as you patiently wait for the fainter Aquarids to appear. In late July the moon will be a waxing crescent and gibbous phase and will set before the best viewing times of the SDA's.

While the Perseids provide more activity, their rates will be tempered by a bright gibbous moon in August. The Delta Aquarids will provide a good show in impressive dark skies so make it a point to try to view this activity. If you are unable to view on the morning of the 30th, rates will nearly be as good on the weekend of August 1/2. Unfortuantely lunar interference increases as you approach the August 6th full moon.

Be sure to share your data with our section coordinator Robert Lunsford.

Viewing Activity from the 2009 Perseid Meteor Shower

The best time for viewing meteors during the northern hemisphere's summer months is during the Perseid meteor shower. This shower is active during the second half of July and throughout most of August. It is most active near August 12, when the Earth passes near the core of the Perseid material. Viewing conditions for this shower depend on the observer's latitude and the phase of the moon on August 12. This activity is visible over most of the Earth except for the extreme southern hemisphere, where the radiant never rises above the horizon. There are also problems viewing this activity from extreme northern latitudes as the nights are very short this time of year. The optimum latitudes lie between 20 and 40 degrees north latitude where the Perseid radiant can achieve a favorable altitude above the horizon and the length of total darkness is at least 6 hours long.

The moon can also cause problems when it is in the sky during viewing hours. If the moon is at its old, new, crescent or first quarter phase, then it will not cause problems. When it is a waxing gibbous, full, waning gibbous, or last quarter, the bright moonlight will obscure the fainter Perseids, reducing the number of meteors visible. Unfortunately in 2009, the moon will be a waning gibbous phase, meaning it will rise late in the evening and will remain in the sky the remainder of the night. This will reduce the Perseid activity by at least half in 2009. So instead of seeing 60 Perseids per hour one may only view 30 per hour this year. Still, this will be one of the more impressive displays of meteoric activity in 2009 as only the Geminids of December are a sure bet to surpass these rates.

The best strategy for viewing Perseid activity this year would be to observe during the last few dark hours before dawn on the morning of August 12. If August 12 is cloudy, decent counts may still be seen on the 11th and 13th. You may try to view during the early evening hours, when the moon is still below the horizon. Unfortunately at this time the Perseid radiant lies low in the north and only a fraction of the overall activity can be seen. The Perseid meteors that are visible this time of night are often spectacular as they streak long distances across the sky and last for several seconds. It's unfortunate that they are so few and far between.

During the morning hours the Perseid radiant rises higher into the sky, allowing more activity to be seen. This year it will be important to make sure to keep the bright moon out of your line of sight. This will allow you to see the most activity. It is also advisable to look approximately half way up into the sky and not straight up. This angle will also allow you to see more activity since the column of air you are viewing through will be thicker at 45 degrees altitude compared to straight up.

While the 2009 Perseid shower is compromised, meteor observers can look forward to 2010 when the moon will be just past its new phase and completely out of the way by the time the Perseid radiant is high in the sky. If you would like to contribute more to our knowledge of the Lyrids, then I invite you to get serious about meteor observing and to make an hourly count of the activity you witness. Other more detailed projects include the estimating the magnitude, velocity, and color of each meteor. Others also note whether there was a persistent train after the meteor has vanished. Meteor watching can be both fun and scientifically useful endeavor. To be scientifically useful you must share your data with an active meteor organization such as the the AMS. We accept data from observers with all levels of experience. The easiest way to send in observations is to email your data to our section coordinator Robert Lunsford. We look forward to hearing from you!

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New Meteors Book by ALPO Meteors Recorder Robert Lunsford

The focus of this book is to introduce the novice to the art of meteor observing. It explains in straightforward language how best to view meteor activity under a variety of conditions, regardless of the observer’s location. The observing conditions for each meteor shower are vastly different from each of the Earth's regions and this book would be valuable to any potential observer from Australia to Alaska. The calendar chapters list activity as it occurs throughout the year. The list is limited to showers that the amateur observer can actually see (some sources list radiants that are impossible to observe without photographic or video methods). Not only are the annual showers discussed, but the random sporadic meteor activity is also included for each region. This is important, as there are many more nights throughout the year when the sporadic background will provide more activity than that provided by the annual showers!...more on http://springer.com/978-0-387-09460-1

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Additional On-Line Resources (Provided by the American Meteor Society)

• Frequently Asked Questions about Meteors and Meteor Showers, a FAQ sheet containing more in-depth information on this topic.

• Robert Lunsford's Weekly Meteor Outlook, a weekly newsletter describing the meteor shower activity for a given week.

• Fireball Reporting Form, Report exceptionally bright fireballs.

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Comments and Questions may be directed to the Meteors Section Coordinator: Robert Lunsford

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Last Modified: May 23, 2009