August 11/12 Meteors

The Perseids continue to increase in strength as we are now within 24 hours of its predicted maximum.

There were a lot of thunderstorm building up during the afternoon and I was worried about the possibility of debris clouds wrecking the night. But my fears were not warranted as the sky was crystal clear for most of the night.

Rates were at least twice as high as they were the night before. Two nights ago my visual observations produced an apparent hourly rate of ~10 per hour which corresponded with a ZHR of 25. Last night I saw ~19 per hour for a ZHR of 50. In addition to the Perseids I also detected ~6 non-Perseids per hour last night which is  down from the 8 per hour seen the night before. These observations were made between 3:14 and 4:39 am (10:14 to 11:39 UT) under a +5.5 limiting magnitude sky.

Each camera also recorded a large increase in meteor from the night before. The wide-field camera detected 51 Perseids versus 27 for the night before. The smaller field SALSA3 camera picked up 63 versus 25 for the night before.

The graph below shows the number of Perseids detected by the SALSA3 camera during the entire night. The histogram is presented in 15 minute intervals. Though the Perseid radiant is above the horizon during the entire night and Perseids should be theoretically visible at any time, the evening hours don’t produce many Perseids. The action really doesn’t get going till after 11 pm and doesn’t get real interesting until after 2 am. Also note that the Perseids, like many showers, is clumpy. This means the meteors come in bunches. Some early morning 15-minute intervals only saw 1 meteor while others saw 6.

This one is for Fred who asked how the MetRec software I use determined which shower a meteor belongs to. The program detects the meteor and measures its position on each video frame. It then extrapolates the meteors path backwards. If the path passes within 10° of an active radiant and the meteor was traveling a reasonable speed to be from that radiant then it is identified as a shower member. Below is a plot of the backwards paths of the Perseids from last night’s SALSA3 data. It is rather apparent that many of last night’s meteor originated from the same point on the sky which just happens to be the radiant of the Perseids.

Worldwide observers are reporting ZHRs of ~50. Based on the last few years, the Perseids should produce at least as many meteors tonight as they did last night and there is a good chance that they will produce even more.

Obs  Date(UT)      Time    TOT SPO ANT PER SDA BPE ERI KCG AUD
SAL3 2010-08-12   08h 22m   97  25  4   63  3   2   0   0   0
ALLS 2010-08-12   08h 38m   63  3   1   51  2   5   1   0   0
VIST 2010-08-12   01h 32m   33  8   -   25  -   -  (LM = +5.5)

SAL3 - SALSA3 camera in Tucson (Carl Hergenrother)
ALLS - Near all-sky camera in Tucson (Carl Hergenrother)
VIST - Visual observations from Tucson (Carl Hergenrother)
SDG - Camera in San Diego operated by Bob Lunsford
Time - Total amount of time each camera looked for meteors
TOT - Total number of meteors detected
SPO - Sporadics (meteors not affiliated with any particular meteor shower)
ANT - Antihelions
PER - Perseids
SDA - Southern Delta Aquariids
BPE - Beta Perseids
ERI - Eta Eridanids
KCG - Kappa Cygnids
AUD - August Draconids