Tables

Abbreviations and observing tables

• α, δ: Coordinates for a shower's radiant position, usually at maximum. α is right ascension, δ is declination. Radiants drift across the sky each day due to the Earth's own orbital motion around the Sun, and this must be allowed for using the details in Table 6 (page 23) for nights away from the listed shower maxima.
• r: The population index, a term computed from each shower's meteor magnitude distribution. r = 2.0 —2.5 is brighter than average, while r above 3.0 is fainter than average.
• λ: Solar longitude, a precise measure of the Earth's position on its orbit which is not dependent on the vagaries of the calendar. All λ are given for the equinox 2000.0.
• v_∞: Atmospheric or apparent meteoric velocity, given in km/s. Velocities range from about 11 km/s (very slow) to 72 km/s (very fast). 40 km/s is roughly medium speed.
• ZHR: Zenithal Hourly Rate, a calculated maximum number of meteors an ideal observer would see in perfectly clear skies with the shower radiant overhead. This figure is given in terms of meteors per hour. Where meteor activity persisted at a high level for less than an hour, or where observing circumstances were very poor, an estimated ZHR (EZHR) is used, which is less accurate than the normal ZHR.
• TFC and PFC: Suggested telescopic and small-camera photographic field centres respectively. β is the observer's latitude (“<” means “south of” and “>” means “north of”). Pairs of telescopic fields must be observed, alternating about every half hour, so that the positions of radiants can be defined. The exact choice of TFC or PFC depends on the observer's location and the elevation of the radiant. Note that the TFCs are also useful centres to use for video camera fields as well.

Table 4. Lunar phases for 2006.

Table 5. Working list of visual meteor showers

Details in this Table were correct according to the best information available in April 2005. Contact the IMO's Visual Commission for more information. Maximum dates in parentheses indicate reference dates for the radiant, not true maxima. Some showers have ZHRs that vary from year to year. The most recent reliable figure is given here, except for possibly periodic showers that are noted as “var.” = variable. An asterisk (“*”) in the “λ” column indicates the shower may have other or additional peak times, noted in the text.

Table 6. Radiant drift positions during the year in α and δ

Table 7. Working list of daytime radio meteor streams

The 50°N and 30°S "Best Observed" columns give the approximate local mean times between which a four-element antenna at an elevation of 45° receiving a signal from a 30 kW transmitter 1000 km away should record at least 85% of any suitably positioned radio-reflecting meteor trails for the appropriate latitudes. Note that this is often heavily dependent on the compass direction in which the antenna is pointing, however, and applies only to dates near the shower's maximum.

Useful addresses

For more information on observing techniques, and when submitting results, please contact the appropriate IMO Commission Director