AMERICAN METEOR SOCIETY, Ltd.
Dr. David Meisel, Executive Director
Department of Physics and Astronomy
State University College
Geneseo, NY, 14454
The main visual observation programs for the AMS Ltd. at present are:
Observers are presumed to know how to protect themselves against cold, moisture, and insect pests, in their own localities. Mosquitoes are particularly objectionable in summer and frostbite in winter. In fall and spring moisture and dew are problems. Minimum equipment for comfort is a deck chair and a sleeping bag. A red-colored flashlight, pencil, clipboard, and watch are minimum equipment for recording. Observing locations away from artificial lights with treeless horizons are ideal, but usually hard to achieve. If lamps have to be present, incandescent lamps are usually preferable to mercury lamps. Locations where electrical power is available may be preferable to the ideal in order to conserve battery power. It should be noted that relatively inexpensive power inverters (these change D.C. car battery current to A.C.) are now available so that A.C. can be provided at remote locations at relatively low cost from car or tractor batteries.
When using a watch to tell the time, it is recommended that a time check by telephone or radio be made just before going out and just after coming in. The shortwave time services CHU and WWV are especially suitable for this. (Some observers simply take a transistor portable radio into the field and listen through an earphone.) These shortwave stations can usually be heard on 2.5, 5, 10, 15 mHz (WWV) or 3.33, 7.335, or 14.670 mHz CHU. There will be days, however, when ionospheric disturbances will prevent good continuous reception of these signals and some other system will be needed. At night it is the lower frequencies that will provide the best reception. Some observers who are not doing plotting are using portable tape recorders (the cassette types are now relatively inexpensive) and verbally note the required meteor information without taking their eyes off the sky. Observers using this method should always put "electronic voice recording system used" on their report forms. It should be noted that recording failures can occur when tape units are used unattended in the dark. In addition, difficulties with the very thin 1/4 mil extended play magnetic tape (also in 120 minute cassettes) are often encountered. These problems range from stretching and skipping to "print through." It should also be noted that it is sometimes difficult to understand the voices on transcribing the data to the report form.
Certain observers (including some of our best) forsake the monotonous time-signals and prefer to record data manually with plots and use their radios to listen to all night music shows. (We presume it can help keeping observers alert, but we trust earphones are used so family and neighbors are not disturbed.) To each his own!
Manual recording can on occasion present difficulties particularly in very cold weather. We would recommend that for extremely cold weather observers always consider their personal safety first, and never exceed their own limitations. It is better to lose data than hands and feet. One way to combat cold hands is to build a glass-topped wooden box with hand-holes that are cloth-lined. Such boxes can be provided with a foot-operated light switch and installation of a glass-enclosed aquarium heater provides safe heat to the interior of the box. (Be careful if the glass protection is scratched or cracked.) Of course, the glass-topped lid should be hinged so that charts, watch, and pencils can be removed easily after completion of observing. A strap on the bottom to hold the box in position on the deck chair is also recommended. If the box cannot be battery powered, A.C. power cords will need to be extended to the observing site. In warm weather, the thermostat on the aquarium heater can be readjusted to provide defrosting for the glass lid. Under unusual moisture conditions, an ice scraper and/or window cleaning cloth should be kept handy. A metal box should never be used because of possible shock hazard and poor thermal insulation. A polystyrene box may be satisfactory provided you are sure the material is fireproof. The mechanical stability of polystyrene however, is questionable.
In the winter, it is essential that the observer keep warm. Electrically heated socks, gloves, and shirts are available. (These are to be battery powered, but such an arrangement is very costly.) These items are usually intended for hunters who must keep mobile. For meteor observers, these can be attached to low voltage (never exceed six volts D.C.) power supplies with rheostats and used safely, provided all bare leads are properly insulated. A sleeping bag and a deck chair (with an air mattress) provide additional comfort.
Sometimes observers are too comfortable and fall asleep. Although coffee and other stimulants are frequently used to stay awake, we do not recommend such measures on a continuous basis. Instead it is recommended that observers "pre-nap" by amounts at least equal to their planned observing run. (Ear plugs and eyeshades may be necessary to insure the pre-nap is undisturbed.)
Although most observers prefer to work when something is happening (i.e. during a known meteor shower), much of our important data is collected on nights when there are no major showers. Thus any moonless night between 10:00 p.m. and dawn (local standard time) is optimum for routine observations. If there is some reason to observe under other circumstances (predicted heavy shower activity, for example) it is certainly acceptable to do so. Because most meteor observers do not start early in the evening (Prior to 10:00 p.m) when the normal rates are low, we still encourage observers, who can, to try to obtain evening hourly rates as the data are needed for statistical purposes.
(a) Major Showers. There are ten major meteor showers that over the years have provided consistent displays. And while most of these can be seen at rates of 1-2 meteors per night over one or two week periods, their major activity is usually limited to one or two days either side of the dates provided below (these may vary slightly from year to year because of leap year changes and so an astronomical magazine, or annual astronomical handbook should be consulted for the exact dates in a particular year).
Shower Approx. Maxima Rates Quadrantids Jan. 2-3 40 Lyrids Apr. 21-22 15 Eta Aquarids May 5-6 20 Delta/Iota Aquarids July 29-30 20 Perseids Aug. 11-12 50 Orionids Oct. 21-22 25 Taurids Nov. 4-5 15 Leonids Nov. 16-17 15 Geminids Dec. 12-13 50 Ursids Dec. 22-23 15Hourly counts (starting on the hour if possible) are always welcome. Plots except by the most experienced observers or for testing purposes (see previous section) are not recommended because of the high numbers sometimes encountered and the likelihood of missed events.
(b) Minor Showers. A meteor shower radiant of some kind has a maximum on about 60 nights out of the year. However, since these are rarely seen producing meteors at rates which significantly exceed the sporadic (random) background rates, they are not generally listed in reference books. These minor showers are sometimes so weak that they are not seen even year-to-year by experienced observers. We will list here, however, dates when minor showers have been observed at maximum, but for reasons of statistical objectivity we will not list the radiants that have been seen in the past around these dates:
(c) Fluctuations of Meteor Shower Rates. Meteor shower rates fluctuate by a considerable amount because meteors even in showers are statistically independent events. Thus when handbooks list hourly rates these are always averages . By certain laws of statistics in any specific instance of counting there will be fluctuations even if the shower itself is "steady". Unusual changes in shower activity can be said to occur only when the actual hourly count is outside the range given by the inequalities below:
where No is the average hourly rate, N is the observed average hourly rate. For minor meteor showers, the above are very important. Suppose No = 4/hr, then the range of counts possible are between 2/hr and 6/hr. If the rate is No = 2/hr, then an N between 1/hr and 3/hr would not be abnormal. For the Perseids, where No = 50/hr, the rates can be as low as 43/hr or as high as 57/hr. Finally in the sporadic rates the same fluctuations occur. Thus, if No = 7/hr the sporadic rates might be as high as 9/hr or as low as 5/hr. The difficulties of detecting a minor shower above the background are illustrated by the following example:
Minor shower: No = 10/hr 13/hr > N > 7/hr Sporadic rate: No = 5/hr 7/hr > N > 3/hrIt can be seen that although on the average the shower is twice the background there will be times when the shower will be nearly swamped by the background.
A second problem with rates is their diurnal sensitivity: (a) the maximum rate is never reached when a radiant is low in the sky, (b) the maximum rate is never reached if the peak occurs at a time when the observer is in daylight, (c) the maximum rate is never reached for showers which cover several days unless the observer persists to the early morning hours and the radiant is still high at that time. For most major showers, few meteors are seen before midnight (local time) and sometimes few can even be seen before 2:00 a.m. (local standard time).
(d) Discovery or Recovery of Meteor Showers. One of the most important things meteor plotting produces is a constant check on the minor showers--old and new. On occasion, even new major showers are discovered in this way. In this regard it is not numbers which count but accuracy of positioning with respect to the stars. Any night without moonlight is suitable and while more meteors are seen after local midnight there are minor showers whose radiants are high in the evening sky and some that can be monitored all night.
Learning the star groups is a skill that meteor observers must master. Constant practice is a must. A computerized planetarium program, if available, is suitable when the weather is bad, but there is no substitute for the real sky. Although we do prefer individual work, we recognize that sometimes group observing is necessary, particularly when observers are young and just starting, since travel to lonely spots may be involved. When such group travel is planned, always make sure local authorities and landowners know your purpose and you have permission to use your chosen site. If your group is affiliated with a local astronomical society, then it is always a good idea to have your sponsors make the necessary arrangements in advance. If a "junior" group has an adult advisor who is willing to go with you on your early morning jaunts, much needless anguish and possible misunderstanding can be avoided.
The results obtained by groups may be submitted together to the AMS Ltd., but for statistical validity, we must assume and insist that each individual honestly report on his own work. The temptation to shout "Did you see that one?" must be avoided if there is a desire to do mature and useful group meteor work. If such incidents do occur occasionally during an observing session, there is no need for concern, but we would appreciate being warned that some bias of this nature may exist in the results. If observers do not warn of possible bias there is no recourse but to reject the data for inclusion in statistical analyses.
Fireballs - In the past, the AMS Ltd. was intensely interested in receiving reports of fireballs. However, in recent years the expense of following up such reports has become prohibitive. We now refer all fireball reports to the Fireball Data Center of the International Meteor Organization. Individual members who have been previously contacted by a regional coordinator should follow his instructions. Otherwise, individuals can fill out the official AMS Ltd. form and mail it promptly to AMS, Ltd. Headquarters. Note we do not have the mandate or resources to track down meteorite falls.
Routine Programs - There is generally no hurry for reporting results of a routine nature. Submission at quarterly or annual intervals are usually sufficient. Notes of unusual meteor activity can be relayed to Meteor News for prompt publication. In the event that the unusual activity may be of interest to professional astronomers, copies of reports to Meteor News can be sent for evaluation to AMS Ltd. headquarters and the executive director will take appropriate action. Although some AMS Ltd. observers have embarked on active telescopic meteor programs, the large bulk of our telescopic data in the past has come from observers doing other work (variable stars, comets, planetary observing, etc.). Therefore, we suggest that the telescopic meteor reports need be submitted only annually.
Meteor Forms - The AMS Ltd. forms have been designed to enable observers to record in a convenient way the data we need to have. We will accept, of course, data on other forms but publish only if the essential data are given. The minimum information for routine meteor count reports is :
Name, address, date, year, and type of time used (E.S.T., E.D.T., G.M.T., or other), location [longitude, latitude or town, (or county,district) plus state and country] For each hour: begin time, end time, total meteors, total number of shower meteors, number of sporadic meteors, average fraction of clear sky, and average limiting star magnitude in zenith.