(meteorobs) Perseids follow-up

[Bruce McCurdy]

    Finally have a minute to follow-up on last week's abbreviated report 
from Cypress Hills Dark Sky Preserve. It turned out that the three-hour 
window that we got the first night (Wed-Thu the 12-13) provided the only 
observing of the entire Saskatchewan Summer Star Party / RASC General 
Assembly weekend. While the weather was disappointing to the vast majority 
of the 402 registrants, from the perspective of meteor observation that 
window could hardly have been better timed, given the outburst which 
occurred around 6h UT. Indeed, with a start time of 0427 and a finish of 
0733, my observing session was exactly centred on 0600 UT!

    After a late night abortively chasing the first outburst here in 
Edmonton, just 2.5 hours sleep, and an 8-hour drive to Cypress Hills I was 
concerned I might just crash out early, but the action was sufficient to 
render me fully awake and alert for the first 2+ hours. It was perhaps the 
finest display of Perseids for me since Mount Kobau in 1994. Right from the 
beginning and despite the low altitude of the radiant I was impressed with 
both the quantity and quality of meteors. Virtually all were trained, to the 
point that I made a note on my digital voice recorder when I finally saw 
one -- my 28th of the night! -- that wasn't. The brightest Perseids featured 
persistent trains of 5 to 20 seconds. Most of these occurred in the hour 
leading up to 06:00, after which the numbers of raw meteors continued to 
ramp up (despite a dip in limiting magnitude after moonrise and increasing 
cloud obstruction) but the average magnitudes diminished. I finally had to 
stop due to cloud obstruction at 06:45, and while it opened up again a 
little later I had mentally started to power down and managed just two 
shortened intervals between 07:10 and 07:33 before calling it a night. By 
that point, meteors were still fairly plentiful but the numbers of bright 
ones had clearly diminished, and my exhaustion started to catch up with me.

    Here's a summary:

Interval **** # PER ** Mean ** Brightest
--------------------------------------------
0427-0441 *** 13 *** +1.2 *** -2
0442-0456 *** 13 *** +1.6 *** -2
0457-0511 *** 12 *** +1.0 *** -1
0512-0526 **** 8 *** +0.5 *** -3
0527-0541 *** 12 *** +0.7 *** -6
0542-0600 *** 15 *** +0.9 *** -6    (inc. 4 min. break)
0601-0615 *** 19 *** +1.7 *** -4
0616-0630 *** 22 *** +1.6 *** -2
0631-0645 *** 14 *** +1.7 *** -3

0710-0720 *** 10 *** +1.4 *** -2
0724-0733 *** 12 *** +2.3 *** 0

    With 168 total meteors over 2.6 hours Teff I'll spare you the full 
play-by-play account, but will list below the 27 negative-magnitude meteors 
I recorded. Note that "~" is my shorthand for the duration of a persistent 
train. The highlight occurred at 0542 when I saw Perseids of mag -6 and -3 a 
few seconds apart, which for several seconds left two fading trains 
diverging from the radiant and separated by about 20-30 degrees.

0427 PER -1
0434 PER -1
0441 PER -2
0451 PER -2
0504 PER -1
0510 PER -1, ~2s green
0517 PER -2, ~3s
0521 PER -3, ~5s off-white
0524 PER -1, bronze
0527 PER -6, ~15s
0535 PER -3, ~5s
0542 PER -6, ~20s
0542 PER -3, ~5s
0543 PER -1, orange
0605 PER -2
0610 PER -2
0613 PER -4, ~10s
0617 PER -1, orange
0621 PER -2, ~3s
0621 PER -1
0624 PER -1
0630 PER -1, bronze
0635 PER -3
0635 PER -1
0639 SDA -2

0710 PER -2, orange
0720 PER -1

   The weather got steadily worse in the subsequent days and nights. Plans 
for my Friday evening meteor clinic went from "under the stars" to "under 
the clouds" to "in a tent out of the rain" to "can't find the tent through 
the fog", and the clinic was ultimately cancelled. Maybe next year!

    Bruce
    *****

PS: Congrats to Esko Lyytinen, Jeremie Vaubaillon, Mikhail Maslov, and Joe 
Rao for their predictions which collectively seem to have nailed those two 
outbursts.