Draconids 2011: visual data quicklook

The graph below shows the ZHR (Zenithal Hourly Rate), which is the number of meteors an observer would see under a very dark sky with the radiant of the shower in zenith.
ZHR_max = 304 based on 6948 Draconids reported in 1807 intervals, assuming population index r = 2.8

The reported intervals are automatically added together into the bins shown above, based on the number of meteors and the distribution of the intervals. For each bin, the following parameters are computed:

• Time is the averaged centre of the reported intervals in Universal Time (UTC);
• Solarlon is the astronomical position of the earth relative to the sun at the above time (equinox J2000.0);
• nINT is the number of reported intervals used;
• nDRA is the number of Draconids observed in those intervals;
• ZHR is the Zenithal Hourly Rate, defined as (1 + sum nDRA) / sum(Teff/C) where Teff is the effective observing time and C is the total correction coefficient for limiting magnitude, clouds and zenith correction 1/sin(h_R); note that the '1+' comes from statistical considerations and will be explained in the next issue of WGN;
• Particle density is the approximate number of particles (meteoroids) causing meteors brighter than magnitude +6.5 per billion cubic kilometer (i.e., a cube with 1000 km edge length). The ZHR depends on this density (which can be variable) and the velocity (which is roughly constant) of the meteoroid stream. For more information about the computation method, see the references at the bottom.

Data has been received from 128 observers in 28 countries. Thank you for your efforts!

Spatial distribution of observers

Note: click on the map for an interactive version.