August 10/11 Meteors
August 11, 2010 2 Comments
This blog and I were highlighted in a University of Arizona press release on the Perseids. For those who found this site through the release, welcome and let’s hope the monsoon rain holds off for another two nights. Then let’s hope it comes back afterwards since we really need the rain.
Another nice night of meteors… This time I actually got up and watched from my backyard for 1.5 hours. With a limiting magnitude of +5.6 (that’s for the faintest visible stars and not for the meteors which were all brighter than about magnitude +4), I saw 26 meteors of which 14 were Perseids. My observing was cut short when a family of ~6 raccoons dropped by to eat some food I left out for one of my cats. For awhile I wasn’t sure what they were and was worried they were a pack of javelina. By the time the raccoons left the sky was brightening.
Based on my visual observations and those of others, the Perseids had a ZHR of ~20-25. For my moderately bright sky that worked out to a rate of ~9 per hour. Since I was also seeing ~8 non-Perseids per hour as well, the total rate was ~17 per hour. The number of Perseids should double over the next 2 nights and maybe even triple or quadruple.
Interestingly 6 of the Perseids were observed in a short 5 minute interval. That’s the thing about these showers, you can go tens of minutes with little activity and then ‘bam’ one after another for a short while.
The wide-field and small-field cameras detected 42 and 57 meteors, respectively. Note the strong difference in the number of non-shower meteors (called Sporadics) with 24 being seen by the smaller field but much more sensitive camera and only 3 picked up by the wide-field camera. Showers are dominated by larger particles because the smaller ones are preferentially removed from the shower trail by the solar radiation forces. These smaller particles end up in the Sporadic population. So it isn’t a surprise that the wide-field camera which only detected bright meteors, finds so few Sporadics.
Obs Date(UT) Time TOT SPO ANT CAP PER SDA BPE ERI KCG AUD SAL3 2010-08-11 08h 01m 57 24 3 1 25 1 2 1 0 0 ALLS 2010-08-11 09h 16m 42 3 0 0 27 2 9 1 0 0 VIST 2010-08-11 01h 32m 26 12 - - 14 - - (LM = +5.6) 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 - Antihelion CAP - Alpha Capricornids PER - Perseids SDA - Southern Delta Aquariids BPE - Beta Perseids ERI - Eta Eridanids KCG - Kappa Cygnids AUD - August Draconids