The Geminids of 1999 again proved that the Geminids are the most reliable and most active annual shower. The shower is known for good activity spanning almost a week. The top rates this year reached almost 140 meteors per hour!!
Three MBK Team members (KACJA, ATAJU and ZAKJU) monitored the activity on two nights - one prior to the peak and the peak night. The first night was December 11/12, with only KACJA and ATAJU observing. The rates were around 15 GEM/h, with LM between +6.5 and +7.0!
The peak night proved to be the best meteoric display on MBK Team record - the observers were split into two groups.
The first group (ATAJU and ZAKJU) was observing from Mariborska Koca, starting at 20:10 LT and observing until 5:40 LT. The sky was extremely transparent and after the moon set the LMs plunged. The average LM was +7.1, while the top average counts were around +7.3! This was probably caused by a patch of extremely dry air passing over us and fog developing in the low lying areas, blocking the light pollution. The number of Geminids was tremendous! Jure Atanackov observed 139 GEM between 3:15 and 4:15, while the same hour Jure Zakrajsek saw no less than 104 GEM! Also the sporadic rates were quite hight, mostly due to the excellent LM, as sometimes they reached over 25/h! Excellent display with Geminids appearing in groups of up to 4 meteors simultaneously! Top minute count came at 22:58 local, with 11 Geminids in a single minute! Ten (10) fireballs, the brightest being a -7m Geminid low in the east producing a bright flash! In the late morning hours the Geminids were still doing 100+/h, but we had to finish as we were experiencing severe effects of low temperatures (50 cm of snow, -15 degrees C and 15 km/h winds!). In 8.87h teff Jure Atanackov recorded 1120 meteors, while Jure Zakrajsek recorded 855 meteors in 7.68h teff! Truly a memorable night for both observers!
The second group (KACJA with Mihaela Triglav of ADJ) was stationed around 200 km west, at Rakitna. They enjoyed somewhat lesser, although still very good limiting magnitudes between +6.5 and +6.8! The group observed for only three (3) hours due to some work/school restriction the next day. The best hourly count by Javor Kac was 54 GEM/h.
Unfortunately, no fireballs were seen by this group, but several -2m meteors were recorded.
Combined analysis with IMO show that the peak, in spite of high rates recorded at Mariborska Koca, did not occur over Europe. The ZHR values of the MBK Team and IMO agree fairly well - Europe saw the ascending part of Geminid activity with the ZHR going from 70 to 100, with the peak value of 135 occuring at 14:00 UT, best seen from Hawaii. The peak time of 14:00 UT also corresponds to an observed increase in the number of fireballs. The ZHR value of 135 is very high even for this strong shower.
Chart 1 - IMO ZHR with the MBK Team ZHR superimposed.
MBK Team could not observe the following night due to bad weather conditions, but global analysis of IMO shows the typical fast decline in rates after the peak, with the ZHR dropping from 135 to 20 in just a day.
Chart 2 - ZHR graph of individual MBK Team members using 15 minute counts. The activity appears to have been quite level for the first part of the night, except around 23:00 LT when a pronounced surge in ZHR occured, with ZHR going up to 120 - 180. In the second part of the night the ZHR is higher, at around 100.