August 12/13 Meteors (and the Peak of the 2010 Perseids)

Last night marked the peak of the Perseids and they didn’t disappoint. Here in Tucson it was clear for yet another night. Quite a remarkable accomplishment considering it should be the middle of the monsoon. Some light cirrus did drift over the area from the south but it really wasn’t thick enough to hamper observing until the very end of the night.

I spent a total of ~2.25 hrs watching the shower spread over 3 separate outings. The plan was to get some sleep and then wake up early in the morning and drive to darker skies on the edge of town. Instead my wife and I decided to go out for an hour right before we went to bed. Though the radiant was very low we were hoping to catch a few atmosphere grazing Perseids. Even though the limiting magnitude was only +5.4 I counted 15 Perseids and 4 non-Perseids over the hour. That worked out to an average ZHR of ~80 over the course of the session. Pretty good.

After a bit of sleep I went back out for another 0.8 hours of observing. By now there was a lot of thin cirrus to the south. Usually the sky is much darker in the morning at my house but the cirrus kept the limiting magnitude at +5.4. During this session I counted 10 Perseids and 2 non-Perseids. This works out to an average ZHR of only 35. For the night of the peak, this is disappointing.

Deciding that I needed to get away from the city lights, I drove out to the edge of town where the limiting magnitude was +5.8. Luckily the cirrus hadn’t spread to the northern sky so I set up shop looking in that direction. The next 0.5 hours or so saw roughly a Perseid per minute with 33 Perseids and 4 non-Perseids being seen. This corresponds to an average ZHR of ~120 which is almost as good as you can expect from the Perseids. It will be nice to see if other observers noticed such high rates at this time (maybe Salvador and Bob).

Though many observations have yet to filed, preliminary results from last night suggest that the ZHR varied from 50 to 100 (see IMO ZHR Live).

Since I was forced by the cirrus to look directly at the radiant I did notice a handful of Perseids that appeared to radiate from an area a few degrees to the south of the radiant (near alpha Persei). I need to take a closer look at my video data to see if it confirms my impression.

My shallow wide-field and deep small-field cameras picked up 91 and 124 meteors last night of which 80 and 91 were Perseids. SALSA3’s 124 meteors is new personal single camera record for me. This beats January 2/3, 2009’s old record of 107 meteors during the peak of the Quadrantids.

If history is any guide, Perseid rates fall off rapidly after the night of maximum. ZHRs of “only” 20-30 should be expected tonight.

SAL3 2010-08-13   08h 16m  124  25  2   91  3   0   1   0   2
ALLS 2010-08-13   08h 33m   91  2   0   80  2   4   2   1   0
VIST 2010-08-13   02h 17m   68  10  -   58  - (LM = +5.4,+5.8)

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


  1. “If history is any guide, Perseid rates fall off rapidly after the night of maximum” – what history exactly? After the question of what to expect during the following night came up here in Germany I looked up the – automatically generated – ZHR(t) plots for the past three years available at and didn’t see the slow-ramp-up-fast-decline pattern at all that everyone (including myself) always takes for granted. And indeed, some 24 hours after the max the ZHR was still in the 50s this year, as the real-time IMO data as well as my own observations from Germany around midnight UTC last night (wildy extrapolated from 11 PER/h) show: about half the maximum value. Makes me wonder whether there is a ‘typical’ ZHR(t) curve for the PER – and other major showers – and what it actually looks like.

    1. Hi Daniel,

      Based on the ZHR Live data for the past 3 years, the rate usually falls to ZHRs of 20-30 on August 14 UT. 2007 did have higher rates of 50 at the start of the 14th but those fell to ~20-30 by mid-date. Still this is based on calendar data and not time from maximum which can shift by up to a day depending on the year.

      My video rates from last night were slightly better than those from the 11th suggesting a ZHR of 30-40.

      I still stand with the thinking that rates drop off more quickly then they rise. Still I worry that overstating this may keep people from observing after the maximum.

      – Carl

  2. Hi Carl,

    I’ve now actually ‘done the numbers’, for 2007, 2008 and 2010 (2009 was too ‘spoiled’ by several individual dust trails) and tried to determine when half the maximum rate was reached before and after the peak. Not easy but here goes:

    2007, ZHRmax ~90 on Aug. 12 at 21 UTC (broad peak 12-16 … 13-02 actually). Half rate 11 hours before and 37 hours after the peak. (I don’t remember: Was the prolonged activity caused by a known dust trail?)

    2008, ZHRmax ~130 on 13-02. Half rate 25 hours and again 3 hours before and 4 hours after the peak. Wow, that was fast! But was there a ‘pre-peak’ of half the main peak’s strength?

    2010, ZHRmax ~110 on 12-17. Half rate 6 hours before and 27 hours after the peak. No major special effects by dust trails predicted – so is this the ‘true’ PER profile?

    So in two cases the decline was slower than the rise, in 2007 and 2010 in a pretty pronounced way, while in 2008 there was this pre-peak.

    Now where are all the PER ZHR(t) plots of the past – can one find those in one publication? And how often do individual dust trails distort the curve? Given the enormous public profile of the Perseids, I’m actually eager now to find out what’s going on here …


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