(meteorobs) Pre-peak Perseids from Alberta

BRUCE MCCURDY bmccurdy at shaw.ca
Fri Aug 12 18:04:26 EDT 2011


It's been tough to find a conjunction of my personal schedule with those of the Moon and the weather gods this Perseid season, but I finally got the opportunity to head out to the dark site at Beaver Hills Dark Sky Preserve on Tuesday morning (Aug 9 UT) for a couple of hours. By the time I set up around 2:30 MDT the Moon had made its exit stage southwest and the Milky Way arched overhead in most of its glory. A low aurora was fairly bright but constrained within about 10° of the northern horizon. What a blessed relief it was to be out in the natural world for a spell and away from the so-called "civilized" one. My company consisted of a lone great horned owl hoohoohoo-ing in the distance, a large mammal that startled me by taking a plunge in a nearby lake, and towards the end of my session a pack of exuberant coyotes singing the hallelujah chorus after another successful hunt. I could, however, see the effect of the city swallowing the Cygnus Star Cloud in the west, so I turned my observing chair resolutely east and watched the radiant climb up the sky. Limiting magnitude started around 6.1 with a very consistent SQM reading of 21.00 +/- 0.03, although all too quickly the  Perseid activity was fairly moderate with eight in the first hour and then fourteen in the second. I was favoured to see six Perseids of negative magnitude, with the brightest being -4. I also saw one suspected member of the August Draconids, as well as a couple of members of the southern radiants which are always low-yield up here at latitude 54. The highlight of my session was the appearance of two Earth-grazers from the Eridanid family, including a spectacular streaker of mag -2 which covered close to 40° of sky and left a persistent train that lasted another couple of seconds.  This occurred at 3:12 a.m. and caused me to double-check the coordinates from the Bob Lunsford's weekly outlook (I always print off just the summary in as large a font as will fit on one page so I can glance at it under low light once in a while). After a little mental geometry I determined the radiant must just be rising around that time. Indeed when I later submitted my IMO report it gave a warning that the Eridanid radiant was below the horizon at 3:00 local time with no such warning for 3:30, while a simulation on Starry Night showed pi Eridani, the lower of Bob's reference stars, rising at 3:13. Better yet, just six minutes later came a second Eridanid that crossed a very similar path to the first, first appearing near Jupiter and arching up through Aries and towards Cassiopeia. This one was ghostlier, just mag +2 or so, but again featured a long path and a briefer persistent train. The two meteors were on such similar paths that I was virtually able to rule out "sporadicity" (it's amazing what kind of lingo one can invent in the dark with a voice recorder in hand). It was sweet to see two so similar in such a short time interval. More than made up for the fact I saw just one Perseid in that half-hour bin. I also got two apparitions of the ISS, the first very nearly intersecting Jupiter, along with a satellite glint that was moving so slowly that I correctly ruled out it's being an Iridium flare. This one was higher up than that, but the glint got to be 0th magnitude or so, just next to the very good comparison star Capella. My counts for this session are summarized here: http://vmo.imo.net/imozhr/obsview/view.php?id=9060 I am very hopeful of getting out again for the peak overnight tonight, Full Moon or no Full Moon. BruceMCCBR*****
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